JP2024064435A - Resin composition, cured film of resin composition and manufacturing method thereof, insulating film, protective film, and electronic component - Google Patents

Abstract

[Problem] To provide a resin composition capable of forming a cured film having excellent mechanical strength while having excellent irregularity embedding properties, a cured film of the resin composition and a method for producing the same, and an insulating film and a protective film using a cured film of the resin composition, and electronic components including these. [Solution] A resin composition containing a polyimide resin, an organic solvent having a saturated vapor pressure of 0.5 kPa or less at 20°C, and an epoxy compound, the cured film having a tensile modulus of elasticity of 4.5 GPa or more as measured by a specific evaluation method. [Selected Figure] None

Description

The present invention relates to a resin composition containing a polyimide resin, a cured film of the resin composition and a method for producing the same, an insulating film, a protective film, and an electronic component.

In recent years, electronic components have rapidly become smaller, thinner, and lighter, and semiconductor devices are becoming more highly integrated and smaller accordingly. To accommodate this trend toward smaller size and higher integration, developments are underway including wafer-level packaging (WLP), 2.5-dimensional integrated circuits (2.5D ICs) using interposers, and three-dimensional integrated circuits (3D ICs) in which dies are stacked by thinning wafers and connected by through-silicon vias (TSVs). These methods also pose significant challenges for the materials used in these devices.

Polyimide resins, polybenzoxazole resins, phenolic resins, etc., which have excellent heat resistance, electrical insulation, and mechanical properties, have been used in insulating materials for electronic components, passivation films, surface protective films, interlayer insulating films, etc. for semiconductor devices. Polyimide resins are resins obtained by dehydrating and ring-closing polyamic acids obtained by condensation reactions of tetracarboxylic dianhydrides and diamines.
However, conventional polyimide resins have the disadvantages of high curing temperatures and large post-curing shrinkage. Large post-curing shrinkage leads to large residual stress in the cured polyimide resin film, which causes bending of semiconductor substrates such as silicon wafers. For example, in the next generation of chip configurations used in three-dimensional integrated circuits, silicon wafers need to be thinned to 20 μm or so in cutting-edge applications to meet the requirements for vertical integration. These thin wafers are extremely brittle, and excessive residual stress in the packaging materials used can be very detrimental. Therefore, low curing temperatures and low post-curing shrinkage are important requirements for packaging materials required for new semiconductor packaging technologies such as advanced wafer-level packages.

Patent Document 1 discloses a polyimide resin that uses a diamine with an indane skeleton as a polyimide resin that meets the requirements for packaging materials necessary for new semiconductor packaging technology, such as low-temperature curing, a low linear thermal expansion coefficient, and solubility in environmentally and semiconductor-friendly solvents.

On the other hand, Patent Document 2 describes a polyimide obtained by reacting a tetracarboxylic dianhydride obtained by reacting trimellitic anhydride chloride with 2,2',3,3',5,5'-hexamethyl-biphenyl-4,4'-diol with 2,2'-bis(trifluoromethyl)benzidine, and a cured film of the polyimide.

Furthermore, in the manufacture of electronic components, it is sometimes required to form a flat resin film on a substrate having steps due to metal wiring or the like.
Patent Document 3 describes a photosensitive resin composition for forming a flattening film, which contains an epoxy resin, a phenoxy resin, and a photosensitizer, and the amount of the phenoxy resin is 20 to 60 parts by mass per 100 parts by mass of the epoxy resin. Patent Document 3 describes that it is possible to provide a resin film that can form a flat resin film by itself and can form a through hole with a vertical or forward tapered side surface.

Patent No. 6467433 Patent No. 6165153 International Publication No. 2020/203648

In recent years, for example, InFO (Integrated Fan-Out) wafer-level packaging technology has been developed. This packaging technology replaces the package substrate in a conventional semiconductor package with a high-density rewiring layer, and therefore does not include a resin substrate, making it possible to reduce material costs, reduce thickness, save power, and improve processing speed. This packaging technology is widely used as a 2.5-dimensional package or PoP (package-on-package), and a technology for stacking InFO wafer-level packages has also been developed.
This packaging technology does not include a package substrate, and a high-density redistribution layer can be stacked. Therefore, the material of the high-density redistribution layer is required to have better mechanical strength. Furthermore, the material of the high-density redistribution layer is also required to have excellent unevenness embedding properties that can embed the unevenness of the wiring.
However, materials with superior mechanical strength have poor irregularity-filling properties, and achieving both superior mechanical strength and irregularity-filling properties has been a difficult task.

The material of Patent Document 3 has insufficient mechanical strength.
The polyimide of Patent Document 2 is described as having excellent transparency, high heat resistance, and low linear thermal expansion coefficient, and exhibiting solvent processability (excellent solubility and film-forming ability) with a low hygroscopic solvent, for the purpose of obtaining a substrate to replace a glass substrate. However, the polyimide described in Patent Document 2 has a problem of poor unevenness-filling ability, as shown in the comparative example described later.

The present invention has been made in consideration of the above problems, and aims to provide a resin composition capable of forming a cured film having excellent mechanical strength while also having excellent irregularity embedding properties, a cured film of the resin composition and a method for producing the same, and an insulating film and a protective film using a cured film of the resin composition, and electronic components containing these.

The present disclosure relates to the following [1] to [15].
[1] A resin composition comprising a polyimide resin, an organic solvent having a saturated vapor pressure of 0.5 kPa or less at 20°C, and an epoxy compound, wherein the resin composition produces a cured film having a tensile modulus of elasticity of 4.5 GPa or more as measured by the following evaluation method.
[Evaluation method]
The resin composition is spin-coated onto a glass substrate having a polyimide film (UPILEX (registered trademark) 125S, [5,5'-biisobenzofuran]-1,1',3,3'-tetraone-1,4-phenylenediamine polycondensate, manufactured by UBE Corporation) attached thereto. The spin-coating conditions are adjusted so that the thickness of the cured film of the resin composition finally obtained is 40 μm±5 μm. After spin-coating the resin composition, the substrate is heated on a hot plate at 40° C. for 8 minutes, then at 80° C. for 8 minutes, and then at 130° C. for 8 minutes to dry the solvent. After drying, the substrate is placed in an oven and heated in the atmosphere at 200° C. for 1 hour, allowed to cool to 25° C., and the cured film of the resin composition is peeled off from the substrate to produce a cured film.
A test piece of the cured film cut into a size of 10 mm wide x 150 mm long is used to measure the tensile modulus at 25°C, a stretching speed of 50 mm/min, and a grip distance of 100 mm using a tensile tester.

[2] The polyimide resin contains a structural unit represented by the following general formula (PI):

（一般式（ＰＩ）において、Ａは芳香族環又は脂肪族環を有するテトラカルボン酸残基である４価の基を表し、Ｂは、芳香族環又は脂肪族環を有するジアミン残基である２価の基を表す。）
前記テトラカルボン酸残基として、下記式（ａ－１）で表されるテトラカルボン酸残基及び下記式（ａ－２）で表されるテトラカルボン酸残基を含み、下記式（ａ－３）で表されるテトラカルボン酸残基を含んでもよく、
前記ジアミン残基として、下記式（ｂ－１）で表されるジアミン残基を含み、下記式（ｂ－２）～（ｂ－６）で表されるジアミン残基からなる群から選択される少なくとも１種のジアミン残基を含んでもよく、
全テトラカルボン酸残基中、下記式（ａ－１）で表されるテトラカルボン酸残基の含有割合は３０モル％～９５モル％であり、下記式（ａ－２）で表されるテトラカルボン酸残基の含有割合は５モル％～４０モル％であり、下記式（ａ－３）で表されるテトラカルボン酸残基の含有割合は０モル％～３５モル％であり、
全ジアミン残基中、下記式（ｂ－１）で表されるジアミン残基の含有割合は５０モル％～１００モル％であり、下記式（ｂ－２）～（ｂ－６）で表されるジアミン残基からなる群から選択される少なくとも１種のジアミン残基の含有割合は０モル％～５０モル％である、前記［１］に記載の樹脂組成物。

(In general formula (PI), A represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and B represents a divalent group which is a diamine residue having an aromatic ring or an aliphatic ring.)
The tetracarboxylic acid residue includes a tetracarboxylic acid residue represented by the following formula (a-1) and a tetracarboxylic acid residue represented by the following formula (a-2), and may include a tetracarboxylic acid residue represented by the following formula (a-3):
The diamine residue includes a diamine residue represented by the following formula (b-1), and may include at least one diamine residue selected from the group consisting of diamine residues represented by the following formulas (b-2) to (b-6):
In the total tetracarboxylic acid residues, the content of tetracarboxylic acid residues represented by the following formula (a-1) is 30 mol % to 95 mol %, the content of tetracarboxylic acid residues represented by the following formula (a-2) is 5 mol % to 40 mol %, and the content of tetracarboxylic acid residues represented by the following formula (a-3) is 0 mol % to 35 mol %,
In the total diamine residues, the content ratio of the diamine residue represented by the following formula (b-1) is 50 mol% to 100 mol%, and the content ratio of at least one diamine residue selected from the group consisting of diamine residues represented by the following formulas (b-2) to (b-6) is 0 mol% to 50 mol%. The resin composition according to [1] above.

(In formulas (a-1) to (a-3) and formulas (b-1) to (b-6), * represents a bond.)

[3] The resin composition according to [1] or [2] above, which has a viscosity of 3,000 mPa·s to 7,000 mPa·s at 25°C when the solid content other than the organic solvent is 7 to 13 mass%.

[4] The resin composition according to any one of [1] to [3], wherein the epoxy compound has three or more epoxy groups in one molecule and includes an epoxy compound having a glycidyl amine moiety.

[5] The resin composition according to any one of [1] to [4], wherein the organic solvent having a saturated vapor pressure of 0.5 kPa or less at 20°C is at least one selected from the group consisting of N,N-dimethylacetamide, benzyl acetate, γ-butyrolactone, and isophorone.

[6] A step of applying the resin composition according to any one of [1] to [5] above onto a substrate and drying it to form a coating film;
A method for producing a cured film of a resin composition, comprising a step of heating the coating film to form a cured film.

[7] The method for producing a cured film described in [6] above, wherein the temperature to which the coating film is heated is 150°C or higher and 240°C or lower.

[8] A cured film obtained by curing the resin composition described in any one of [1] to [5] above.

[9] The cured film described in [8] above, having a linear thermal expansion coefficient of 40 ppm/°C or less at 100°C to 150°C.

[10] An insulating film produced using the cured film according to [8] or [9] above.
[11] A protective film produced using the cured film according to [8] or [9] above.
[12] An electronic component comprising the insulating film according to [10].
[13] An electronic component comprising the protective film according to [11].
[14] An electronic component comprising: an IC chip; a molding resin surrounding at least the IC chip; and a wiring layer including the insulating film and wiring of [10].
[15] The electronic component according to [14], wherein the molding resin is a cured product of an epoxy resin composition.

The present invention provides a resin composition capable of forming a cured film having excellent mechanical strength and excellent irregularity embedding properties, a cured film of the resin composition and a method for producing the same, an insulating film and a protective film using the cured film of the resin composition, and electronic components containing these.

FIG. 1 is a manufacturing process diagram of a semiconductor device having a multi-layer wiring structure, which is an electronic component according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a pad portion of a semiconductor device having an insulating film according to an embodiment of the present invention.

The polyimide resin, resin composition, cured film of the resin composition and production method thereof, insulating film, protective film, and electronic component according to the present invention will be described in detail below.
In addition, terms used in this specification that specify shapes, geometric conditions, and the degree thereof, such as "parallel,""orthogonal," and "same," as well as values of length and angle, are not to be bound by strict meanings, but are to be interpreted to include a range within which similar functions can be expected.
In the drawings attached to this specification, the scale and aspect ratios may be appropriately changed and exaggerated from those of the actual objects for the convenience of illustration and ease of understanding.
In addition, in this specification, the use of "to" indicating a range of values is used to mean that the values before and after it are included as the lower limit and upper limit.
In this specification, (meth)acrylic means each of acrylic and methacrylic, and (meth)acryloyl means each of acryloyl and methacryloyl.

I. Resin Composition The resin composition according to one embodiment of the present invention contains a polyimide resin, an organic solvent having a saturated vapor pressure of 0.5 kPa or less at 20° C., and an epoxy compound, and the resin composition has a tensile modulus of elasticity of a cured film of 4.5 GPa or more as measured by the following evaluation method.
[Evaluation method]
The resin composition is spin-coated onto a glass substrate having a polyimide film (UPILEX (registered trademark) 125S, [5,5'-biisobenzofuran]-1,1',3,3'-tetraone-1,4-phenylenediamine polycondensate, manufactured by UBE Corporation) attached thereto. The spin-coating conditions are adjusted so that the thickness of the cured film of the resin composition finally obtained is 40 μm±5 μm. After spin-coating the resin composition, the substrate is heated on a hot plate at 40° C. for 8 minutes, then at 80° C. for 8 minutes, and then at 130° C. for 8 minutes to dry the solvent. After drying, the substrate is placed in an oven and heated in the atmosphere at 200° C. for 1 hour, allowed to cool to 25° C., and the cured film of the resin composition is peeled off from the substrate to produce a cured film.
A test piece of the cured film cut into a size of 10 mm wide x 150 mm long is used to measure the tensile modulus at 25°C, a stretching speed of 50 mm/min, and a grip distance of 100 mm using a tensile tester.
In addition, if the resin composition has a tensile modulus of elasticity of 4.5 GPa or more when the thickness of the finally obtained cured film is within the range of 40 μm ± 5 μm, the resin composition satisfies the condition that the cured film has a tensile modulus of elasticity of 4.5 GPa or more when measured by the evaluation method of the present invention. However, the tensile modulus is basically the same within the range of 40 μm ± 5 μm.

In the evaluation of the tensile modulus, the polyimide film (UPILEX (registered trademark) 125S, manufactured by UBE Corporation, [5,5'-biisobenzofuran]-1,1',3,3'-tetraone-1,4-phenylenediamine polycondensate) used in the substrate when preparing the cured film is used to facilitate peeling of the cured film of the resin composition from the substrate. Therefore, even if UPILEX (registered trademark) 125S, manufactured by UBE Corporation, becomes unavailable, it is possible to use a similar polyimide film instead, as long as the cured film of the resin composition produced by the above-mentioned manufacturing method can be peeled from the substrate without damaging the cured film of the resin composition.
Note that Upilex (registered trademark) 125S manufactured by UBE Inc. is registered under the Chemical Substances Control Law as "[5,5'-biisobenzofuran]-1,1',3,3'-tetraone.1,4-phenylenediamine polycondensate (limited to polyimides) (limited to those having a number average molecular weight of 1,000 or more and insoluble in water, fat-soluble solvents, general-purpose solvents, acids and alkalis)" and has a film thickness of 125 μm.

The resin composition according to one embodiment of the present invention may be referred to as a polyimide resin composition or a polyimide composition because it is a resin composition containing a polyimide resin.
The resin composition according to one embodiment of the present invention contains a polyimide resin, an organic solvent having a saturated vapor pressure of 0.5 kPa or less at 20° C., and an epoxy compound, and the resin composition has a tensile modulus of elasticity of a cured film of 4.5 GPa or more as measured by the above-mentioned evaluation method. Therefore, the resin composition is capable of forming a cured film having excellent mechanical strength and has excellent irregularity filling properties.

The resin composition of the present invention contains a ring-closed soluble polyimide resin dissolved in an organic solvent, instead of a polyimide precursor. Therefore, the resin composition of the present invention does not require heating to a high temperature of 350° C. to convert the polyimide resin into a coating film from the polyimide precursor, and can form a cured film containing the polyimide resin at a low temperature and can suppress shrinkage after curing.
However, the following formula shows that the higher the elastic modulus (the larger the value), the larger the internal stress (shrinkage stress) σ generated during film formation. Thus, since a material with a high elastic modulus and excellent mechanical strength generates a large internal stress (shrinkage stress) during film formation, when a cured film is formed on a textured substrate, gaps are likely to occur near the substrate interface of the recesses, resulting in poor texture-filling properties, and achieving both excellent mechanical strength and texture-filling properties has been a difficult task.

（Ｅ:弾性率、α：線膨張係数）

(E: elastic modulus, α: linear expansion coefficient)

In contrast, the resin composition of the present invention combines a resin with a high elastic modulus with an organic solvent having a saturated vapor pressure of 0.5 kPa or less at 20° C. Organic solvents having a saturated vapor pressure of 0.5 kPa or less at 20° C. evaporate slowly. By combining a resin with a high elastic modulus with a solvent that evaporates slowly, shrinkage proceeds slowly even when a resin with a high elastic modulus is used, making it difficult for gaps to occur near the substrate interface of the recessed portion, and it is presumed that the unevenness embedding property is improved.
The resin composition of the present invention contains a polyimide resin in combination with an epoxy compound. The epoxy group contained in the epoxy compound can react with an amino group, a carboxy group, an acetamide group, or the like at the end of the polyimide resin. By bonding the epoxy compound to the end of the polyimide resin, the polyimide resin can be crosslinked, thereby improving mechanical properties such as tensile modulus of elasticity more than the polyimide resin alone. In addition, by bonding the epoxy compound to the end of the polyimide resin, the epoxy group of the epoxy compound is ring-opened to generate a hydroxyl group. As a result, it is presumed that the resin composition of the present invention can form a cured film of the resin composition having improved adhesion to a plurality of materials such as inorganic compounds and metals while taking advantage of the characteristics of the polyimide resin, such as a high modulus of elasticity and a low linear thermal expansion coefficient. Therefore, it is presumed that the resin composition of the present invention has excellent unevenness embedding properties even when a cured film is formed on an uneven substrate having a structure such as wiring on the substrate.

The resin composition of the present invention contains a polyimide resin, an organic solvent having a saturated vapor pressure of 0.5 kPa or less at 20°C, and an epoxy compound, and may further contain other components as long as the effects of the present invention are not impaired. Each component will be described in turn below.

1. Polyimide Resin The polyimide resin contained in the resin composition of the present invention is selected from soluble polyimide resins that are soluble in organic solvents having a saturated vapor pressure of 0.5 kPa or less at 20°C.
The polyimide resin contained in the resin composition of the present invention may be one that provides a cured film of the polyimide resin alone with a tensile modulus of 4.5 GPa or more. However, since it is sufficient that the cured film of the resin composition containing the polyimide resin and the epoxy compound has a tensile modulus of 4.5 GPa or more, the cured film of the polyimide resin alone does not necessarily have to have a tensile modulus of 4.5 GPa or more.

The polyimide resin contained in the resin composition of the present invention contains, for example, a structural unit represented by the following general formula (PI) in view of its solubility in the organic solvent and its ease of achieving a high tensile modulus:

（一般式（ＰＩ）において、Ａは、芳香族環又は脂肪族環を有するテトラカルボン酸残基である４価の基を表し、Ｂは、芳香族環又は脂肪族環を有するジアミン残基である２価の基を表す。）
前記テトラカルボン酸残基として、下記式（ａ－１）で表されるテトラカルボン酸残基及び下記式（ａ－２）で表されるテトラカルボン酸残基を含み、下記式（ａ－３）で表されるテトラカルボン酸残基を含んでもよく、
前記ジアミン残基として、下記式（ｂ－１）で表されるジアミン残基を含み、下記式（ｂ－２）～（ｂ－６）で表されるジアミン残基からなる群から選択される少なくとも１種のジアミン残基を含んでもよく、
全テトラカルボン酸残基中、下記式（ａ－１）で表されるテトラカルボン酸残基の含有割合は３０モル％～９５モル％であり、下記式（ａ－２）で表されるテトラカルボン酸残基の含有割合は５モル％～４０モル％であり、下記式（ａ－３）で表されるテトラカルボン酸残基の含有割合は０モル％～３５モル％であり、
全ジアミン残基中、下記式（ｂ－１）で表されるジアミン残基の含有割合は５０モル％～１００モル％であり、下記式（ｂ－２）～（ｂ－６）で表されるジアミン残基からなる群から選択される少なくとも１種のジアミン残基の含有割合は０モル％～５０モル％であるポリイミド樹脂であってよい。

(In general formula (PI), A represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and B represents a divalent group which is a diamine residue having an aromatic ring or an aliphatic ring.)
The tetracarboxylic acid residue includes a tetracarboxylic acid residue represented by the following formula (a-1) and a tetracarboxylic acid residue represented by the following formula (a-2), and may include a tetracarboxylic acid residue represented by the following formula (a-3):
The diamine residue includes a diamine residue represented by the following formula (b-1), and may include at least one diamine residue selected from the group consisting of diamine residues represented by the following formulas (b-2) to (b-6):
In the total tetracarboxylic acid residues, the content of tetracarboxylic acid residues represented by the following formula (a-1) is 30 mol % to 95 mol %, the content of tetracarboxylic acid residues represented by the following formula (a-2) is 5 mol % to 40 mol %, and the content of tetracarboxylic acid residues represented by the following formula (a-3) is 0 mol % to 35 mol %,
The polyimide resin may have a diamine residue represented by the following formula (b-1) content of 50 mol % to 100 mol % in all diamine residues, and a diamine residue content of at least one type selected from the group consisting of diamine residues represented by the following formulas (b-2) to (b-6) of 0 mol % to 50 mol %.

(In formulas (a-1) to (a-3) and formulas (b-1) to (b-6), * represents a bond.)

In the polyimide resin, the tetracarboxylic acid residue refers to a residue obtained by removing four carboxyl groups from a tetracarboxylic acid, and represents the same structure as a residue obtained by removing an acid dianhydride structure from a tetracarboxylic acid dianhydride, and may be a tetracarboxylic acid dianhydride residue.
The diamine residue refers to a residue obtained by removing two amino groups from a diamine.

The tetracarboxylic acid residue represented by the formula (a-1) has a specific structure containing a parabiphenylene group with a twisted dihedral angle via an ester bond, and thus, by containing the tetracarboxylic acid residue represented by the formula (a-1), the polyimide resin tends to have an excellent balance of excellent mechanical properties and thermal properties (high tensile modulus and low coefficient of linear thermal expansion), high solubility (low viscosity), and unevenness embeddability due to linear rigidity and moderate reduction in intermolecular force caused by twisting.
Therefore, the content of the tetracarboxylic acid residues represented by the formula (a-1) may be 30 mol % or more, 35 mol % or more, 40 mol % or more, or 50 mol % or more, of all tetracarboxylic acid residues, from the standpoint of mechanical properties and thermal properties; on the other hand, the content of the tetracarboxylic acid residues may be 95 mol % or less, 90 mol % or less, 70 mol % or less, or 60 mol % or less, of all tetracarboxylic acid residues, from the standpoint of high solubility (low viscosity) and irregularity embeddability.

The tetracarboxylic acid residue represented by the formula (a-2) has a rigid structure consisting of a three-ring condensed structure, and therefore can impart excellent mechanical properties and thermal properties to the polyimide resin.
Therefore, the content ratio of the tetracarboxylic acid residues represented by the formula (a-2) may be 5 mol % or more, 10 mol % or more, 20 mol % or more, or 25 mol % or more, of all tetracarboxylic acid residues, from the standpoint of mechanical properties and thermal properties; on the other hand, from the standpoint of high solubility (low viscosity) and irregularity embeddability, the content ratio of the tetracarboxylic acid residues may be 40 mol % or less, or 35 mol % or less, of all tetracarboxylic acid residues.

The tetracarboxylic acid residue represented by the formula (a-3) can incorporate a large bending structure into the polyimide main chain by bond rotation between the carbonyl carbon and the aromatic carbon. Therefore, the introduction of a certain amount of the tetracarboxylic acid residue has the effect of appropriately weakening the intermolecular forces in the polyimide resin, and can improve the solubility (low viscosity) and the unevenness embedding property of the polyimide resin. In addition, since the bending direction of the 3,3',4,4'-benzophenonetetracarboxylic dianhydride residue is fixed by the carbonyl group, it is presumed that the mechanical properties of the polyimide resin are not easily deteriorated.
The polyimide resin used in the present invention may not contain the tetracarboxylic acid residue represented by the formula (a-3) as long as the solubility and irregularity embedding ability of the polyimide resin are ensured.
Therefore, the content ratio of the tetracarboxylic acid residues represented by the formula (a-3) may be 0 mol % or more, 5 mol % or more, or 10 mol % or more, of all the tetracarboxylic acid residues, from the viewpoints of high solubility (low viscosity) and irregularity embeddability; on the other hand, the content ratio of the tetracarboxylic acid residues may be 35 mol % or less, 25 mol % or less, or 20 mol % or less, of all the tetracarboxylic acid residues, from the viewpoints of mechanical properties and thermal properties.

The diamine residue represented by the formula (b-1) has a specific structure containing a parabiphenylene group with a twisted dihedral angle, and has a strong electron-withdrawing property of a trifluoromethyl group. Therefore, by containing the diamine residue represented by the formula (b-1), the polyimide resin is likely to have an excellent balance between excellent mechanical properties and thermal properties, high solubility (low viscosity), and unevenness embedding property due to linear rigidity and moderate reduction in intermolecular force caused by twisting.
Therefore, from the viewpoint of mechanical properties and thermal properties, the content of the diamine residue represented by the formula (b-1) may be 50 mol % or more, 70 mol % or more, 80 mol % or more, or 90 mol % or more, of all diamine residues; on the other hand, it may be 100 mol % or less, 98 mol % or less, or 95 mol % or less, of all diamine residues.

At least one diamine residue selected from the group consisting of diamine residues represented by the formulas (b-2) to (b-6) has a hexafluoroisopropylidene group, an ether group, or a sulfonyl group in its molecular structure, and can incorporate a bent structure into the polyimide main chain. Therefore, by introducing a certain amount, it has the effect of moderately weakening the intermolecular forces in the polyimide resin, and can improve the solubility (low viscosity) and unevenness embedding properties of the polyimide resin. In addition, the hexafluoroisopropylidene group, ether group, and sulfonyl group contained in at least one diamine residue selected from the group consisting of diamine residues represented by the formulas (b-2) to (b-6) are highly polar functional groups, and it is presumed that they are unlikely to reduce the mechanical properties of the polyimide resin because they can suppress excessive weakening of the intermolecular forces.
In the polyimide resin used in the present invention, so long as the solubility (low viscosity) and the ability to embed irregularities are ensured, at least one diamine residue selected from the group consisting of the diamine residues represented by the formulas (b-2) to (b-6) may not be contained.
Therefore, the content of at least one kind of diamine residue selected from the group consisting of diamine residues represented by the formulas (b-2) to (b-6) may be 0 mol % or more, 2 mol % or more, or 5 mol % or more, of all diamine residues, from the standpoints of high solubility (low viscosity) and irregularity embeddability; on the other hand, it may be 50 mol % or less, 30 mol % or less, 20 mol % or less, or 10 mol % or less, of all diamine residues, from the standpoints of mechanical properties and thermal properties.
Among these, a diamine residue having a hydroxyl group, such as the diamine residue represented by (b-2), can react with an epoxy compound. If the diamine residue is contained in a large amount, the crosslinking reaction between the epoxy compound and the polyimide main chain may proceed excessively, resulting in hardness and brittleness and a decrease in the tensile modulus of elasticity. Therefore, the content of the diamine residue may be 40 mol % or less.

In a polyimide resin that contains a structural unit represented by the general formula (PI), includes as the tetracarboxylic acid residues the tetracarboxylic acid residues represented by the formula (a-1) and the tetracarboxylic acid residues represented by the formula (a-2), and may include as the tetracarboxylic acid residues represented by the formula (a-3), and includes as the diamine residues the diamine residues represented by the formula (b-1) and may include at least one diamine residue selected from the group consisting of the diamine residues represented by the formulas (b-2) to (b-6), the polyimide resin may contain other tetracarboxylic acid residues different from the tetracarboxylic acid residues represented by the formulas (a-1) to (a-3) and the diamine residues represented by the formulas (b-1) to (b-6) in the specific amounts, and may contain other tetracarboxylic acid residues different from the tetracarboxylic acid residues represented by the formulas (a-1) to (a-3) and other diamine residues different from the diamine residues represented by the formulas (b-1) to (b-6), as long as the effects of the present invention are not impaired.

Other tetracarboxylic acid residues different from the tetracarboxylic acid residues represented by the formulas (a-1) to (a-3) include tetracarboxylic acid residues derived from at least one of tetracarboxylic acid dianhydrides having an aromatic ring and tetracarboxylic acid dianhydrides having an aliphatic ring.

Examples of tetracarboxylic acid dianhydrides having an aromatic ring that induces other tetracarboxylic acid residues include 2,2',3,3'-benzophenone tetracarboxylic acid dianhydride, 3,3',4,4'-biphenyl tetracarboxylic acid dianhydride, 2,2',3,3'-biphenyl tetracarboxylic acid dianhydride, 2,3,3',4'-biphenyl tetracarboxylic acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, Bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 1,3-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 1,4-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 2,2-bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}propane dianhydride, 2,2-bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}propane dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, 4,4'-bis[4-(1,2-dicarboxy )phenoxy]biphenyl dianhydride, 4,4'-bis[3-(1,2-dicarboxy)phenoxy]biphenyl dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}sulfone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}sulfone dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}sulfide dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}sulfide dianhydride, 4,4'-(hexafluoro 3,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3'-(hexafluoroisopropylidene)diphthalic anhydride, 4,4'-oxydiphthalic anhydride, 3,4'-oxydiphthalic anhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, and the like.
Examples of tetracarboxylic acid dianhydrides having an aliphatic ring from which other tetracarboxylic acid residues are derived include cyclohexanetetracarboxylic acid dianhydride, cyclopentanetetracarboxylic acid dianhydride, dicyclohexane-3,4,3',4'-tetracarboxylic acid dianhydride, cyclobutanetetracarboxylic acid dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, and 1,1'-bicyclohexane-3,3',4,4'-tetracarboxylic acid dianhydride.
These may be used alone or in combination of two or more.

The tetracarboxylic dianhydride from which the other tetracarboxylic acid residues are derived may be at least one selected from the group consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dianhydride, and cyclobutanetetracarboxylic dianhydride, in terms of the excellent mechanical properties of the polyimide resin.

Other diamine residues different from the diamine residues represented by the formulas (b-1) to (b-6) include diamine residues derived from at least one diamine having an aromatic ring and a diamine having an aliphatic ring.

Examples of diamines having an aromatic ring from which other diamine residues are derived include p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, 2,4-diaminodurene, 4,4'-diaminodiphenylmethane, 4,4'-methylenebis(2-methylaniline), 4,4'-methylenebis(2-ethylaniline), 4,4'-methylenebis(2,6-dimethylaniline), 4,4'-methylenebis(2,6-diethylaniline), 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 2,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'-diamino Examples of the amines include diphenyl sulfone, 4,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzanilide, 4-aminophenyl-4'-aminobenzoate, benzidine, 3,3'-dihydroxybenzidine, 3,3'-dimethoxybenzidine, o-tolidine, m-tolidine, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)biphenyl, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, 2,2-bis(4-aminophenyl)hexafluoropropane, and p-terphenylenediamine.
Examples of diamines having an aliphatic ring from which other diamine residues are derived include 4,4'-methylenebis(cyclohexylamine), isophoronediamine, trans-1,4-diaminocyclohexane, cis-1,4-diaminocyclohexane, 1,4-cyclohexanebis(methylamine), 2,5-bis(aminomethyl)bicyclo[2.2.1]heptane, 2,6-bis(aminomethyl)bicyclo[2.2.1]heptane, 3,8-bis(aminomethyl)tricyclo[5.2.1.0]decane, 1,3-diaminoadamantane, 2,2-bis(4-aminocyclohexyl)propane, and 2,2-bis(4-aminocyclohexyl)hexafluoropropane.
These may be used alone or in combination of two or more.

The diamine having an aromatic ring from which the other diamine residues are derived may be at least one of p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, 2,4-diaminodurene, benzidine, 3,3'-dihydroxybenzidine, 3,3'-dimethoxybenzidine, o-tolidine, m-tolidine, and p-terphenylenediamine, from the viewpoint of excellent mechanical properties of the polyimide resin.

In a polyimide resin that contains a structural unit represented by the general formula (PI), includes, as the tetracarboxylic acid residue, a tetracarboxylic acid residue represented by the formula (a-1) and a tetracarboxylic acid residue represented by the formula (a-2), and may include a tetracarboxylic acid residue represented by the formula (a-3), and includes, as the diamine residue, a diamine residue represented by the formula (b-1) and may include at least one diamine residue selected from the group consisting of diamine residues represented by the formulas (b-2) to (b-6), the total content of the tetracarboxylic acid residue represented by the formula (a-1), the tetracarboxylic acid residue represented by the formula (a-2), and the tetracarboxylic acid residue represented by the formula (a-3) in all tetracarboxylic acid residues may be 70 mol% or more, 80 mol% or more, 90 mol% or more, 95 mol% or more, or 100 mol%.
In addition, in the polyimide resin, in order to achieve solubility in the organic solvent, a high tensile modulus, and excellent irregularity embedding properties, the total content of the diamine residues represented by formula (b-1) and at least one diamine residue selected from the group consisting of diamine residues represented by formulas (b-2) to (b-6) in all diamine residues may be 70 mol % or more, 80 mol % or more, 90 mol % or more, 95 mol % or more, or even 100 mol %.

In addition, the polyimide resin containing the constitutional unit represented by the general formula (PI) used in the present invention may have a structure different from the constitutional unit represented by the general formula (PI) in a part thereof, so long as the effects of the present invention are not impaired.
In the polyimide resin used in the present invention containing the constitutional unit represented by the general formula (PI), the total of the constitutional units represented by the general formula (PI) may be 90 mol % or more, 95 mol % or more, 98 mol % or more, or 100 mol % of all constitutional units of the polyimide resin.
Examples of structures different from the constituent unit represented by general formula (PI) include a constituent unit containing a tetracarboxylic acid residue having no aromatic ring or aliphatic ring, a constituent unit containing a diamine residue having no aromatic ring or aliphatic ring, a constituent unit in which the tetracarboxylic acid component is not completely imidized and has a polyamic acid structure in part, a polyamideimide constituent unit containing a tricarboxylic acid residue such as trimellitic anhydride, a polyamide constituent unit, and the like.

The content (mol %) of each residue in the polyimide resin used in the present invention can be determined by confirming the ratio of the raw material composition, for example, by the following method.
First, a sodium hydroxide solution containing 2.0 g of sodium hydroxide, 25 mL of water, and 25 mL of methanol is prepared, and 200 mg of polyimide resin is dissolved in 10 mL of the sodium hydroxide solution. The solution is heated in a pressure vessel at 250° C. for 1 hour to promote depolymerization of the polyimide resin. The resulting solution is extracted with chloroform and water, and the decomposition product (raw material monomer) is separated. The ratio of the raw material composition is measured by gas chromatography (HP6890/HP5973 manufactured by Agilent Technologies) (the column is "InertCap 5MS/Sil (30 m x 250 μm x 0.25 μm, manufactured by GL Sciences Inc.", the measurement conditions are 50° C. for 5 min, then heated to 320° C. at 10° C./min and held for 3 min). The composition ratio of each raw material can be calculated from the area ratio of gas chromatography.
The content (mol%) of each residue in the polyimide resin can be determined from the charge ratio of the raw materials during the production of the resin. The structure of the polyimide resin can be determined using NMR, various mass spectrometry, elemental analysis, XPS/ESCA, TOF-SIMS, etc.

The method for producing the polyimide resin used in the present invention is not particularly limited, but may be, for example, a method for producing a polyimide resin using a tetracarboxylic acid dianhydride represented by the following chemical formula (1-1) and pyromellitic anhydride, and optionally two or more kinds of tetracarboxylic acid dianhydrides including 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride and tetracarboxylic acid dianhydrides having other aromatic or aliphatic rings, 2,2'-bis(trifluoromethyl)benzidine, and optionally 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, 4,4'-diaminodiphenyl It can be produced through a process of obtaining a polyimide precursor (polyamic acid) by reacting at least one diamine selected from the group consisting of bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, bis(4-(3-aminophenoxy)phenyl)sulfone, and bis(4-(4-aminophenoxy)phenyl)sulfone with one or more diamines including, as necessary, a diamine having another aromatic ring or an aliphatic ring, and a process of imidizing the obtained polyimide precursor (polyamic acid).

The tetracarboxylic dianhydride represented by the general formula (1-1) can be obtained by a known esterification reaction using 2,2',3,3'5,5'-hexamethyl-biphenyl-4,4'-diol and trimellitic acids. Examples of the trimellitic acids include trimellitic anhydride and trimellitic anhydride halide. For a method of synthesizing the tetracarboxylic dianhydride represented by the general formula (1-1), refer to Japanese Patent No. 6165153 as appropriate.
The tetracarboxylic dianhydride having an aromatic ring or an aliphatic ring and the diamine having an aromatic ring or an aliphatic ring, which are used as necessary, may be appropriately selected from the above-mentioned tetracarboxylic dianhydride and the above-mentioned diamine, respectively. The method for producing the tetracarboxylic dianhydride having an aromatic ring or an aliphatic ring and the diamine having an aromatic ring or an aliphatic ring, which are used as necessary, is not particularly limited, and a known production method may be appropriately adopted, or a commercially available product may be appropriately used.

The polyimide precursor is obtained by reacting the tetracarboxylic dianhydride with the diamine in a solvent. The solvent used in the synthesis of the polyimide precursor is not particularly limited as long as it can dissolve the tetracarboxylic dianhydride and diamine described above, and for example, an aprotic polar solvent can be used. In the present invention, it is preferable to use organic solvents containing nitrogen atoms such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide; γ-butyrolactone, etc. An organic solvent is a solvent that contains carbon atoms.

The polymerization reaction procedure can be appropriately selected from known methods.
For example, in a low humidity environment by nitrogen substitution, first, a diamine is dissolved in a polymerization solvent in a reaction vessel, and to this solution, a substantially equimolar amount of acid dianhydride to the diamine is gradually added, followed by stirring using a mechanical stirrer or the like at a temperature in the range of 0 to 100° C., preferably 20 to 60° C., for 0.5 to 150 hours, preferably 1 to 48 hours. In this case, the monomer concentration is usually in the range of 5 to 50% by mass, preferably 10 to 40% by mass.

The polyimide precursor solution is prepared by combining at least two kinds of tetracarboxylic dianhydrides. The polyamic acid may be synthesized by adding at least two kinds of acid dianhydrides at once to a polymerization solvent in which a diamine is dissolved, or the at least two kinds of acid dianhydrides may be added in a stepwise manner in an appropriate molar ratio to a reaction solution, thereby controlling to some extent the sequence in which each raw material is incorporated into a polymer chain.
For example, a tetracarboxylic dianhydride represented by general formula (1-1) may be added to a reaction solution in which a diamine has been dissolved, and reacted to synthesize an amic acid in which the tetracarboxylic dianhydride represented by general formula (1-1) and the diamine have reacted, and then pyromellitic anhydride and, if necessary, a tetracarboxylic dianhydride having an aromatic ring or an aliphatic ring may be added thereto, and, if necessary, a diamine may be further added to polymerize the polyamic acid. When polymerized by this method, the tetracarboxylic dianhydride represented by general formula (1-1) is introduced into the polyamic acid in a linked form via one diamine.
Polymerizing polyamic acid by such a method is preferable because it allows the positional relationship of tetracarboxylic acid residues having a specific structure containing a parabiphenylene group with a twisted dihedral angle in the main chain via an ester bond to be specified to a certain extent, the weight average molecular weight as calculated in terms of polystyrene by gel permeation chromatography is likely to be 50,000 or more, and a cured film having excellent tensile modulus and low linear thermal expansion coefficient can be easily obtained.

When the number of moles of diamine in the polyimide precursor solution (polyamic acid solution) is a and the number of moles of tetracarboxylic dianhydride is b, b/a may be 0.9 or more and 1.1 or less, or 0.95 or more and 1.05 or less. In terms of the resolubility of the coating film and the weight average molecular weight calculated as polystyrene by gel permeation chromatography, b/a may be 0.98 or more and 1.01 or less, or 0.99 or more and less than 1.00. By setting the ratio within such a range, the molecular weight (degree of polymerization) of the obtained polyamic acid can be appropriately adjusted, and the functional groups at the terminals can also be adjusted.

In order to prepare a polyimide resin having a desired weight average molecular weight as calculated by polystyrene equivalent using gel permeation chromatography, it is preferable to gradually add an acid dianhydride to a reaction solution in which a diamine is dissolved in the preparation of the polyimide precursor, and carry out the reaction while measuring by gel permeation chromatography that the molecular weight reaches the desired range.

The polyimide precursor (polyamic acid) may have a weight average molecular weight of 50,000 or more, or 60,000 or more, from the viewpoint of obtaining excellent mechanical properties of the cured film of the resin composition. On the other hand, the polyimide precursor (polyamic acid) may have a weight average molecular weight of 100,000 or less, 90,000 or less, or 80,000 or less, from the viewpoint of making it possible to increase the thickness of the cured film of the resin composition and to provide excellent irregularity embedding properties.
The weight average molecular weight of the polyimide precursor can be measured by gel permeation chromatography (GPC).

As the polyimide precursor (polyamic acid) used for imidization, the polyimide precursor solution obtained by the synthesis reaction may be used as is, or the solvent of the polyimide precursor solution may be dried and dissolved in another solvent.

Methods for imidizing a polyimide precursor include thermal imidization, which involves a dehydration ring-closing reaction by heating, and chemical imidization, which involves a dehydration ring-closing reaction using a chemical imidization agent (a dehydration ring-closing agent).Of these, chemical imidization is preferred from the viewpoint of avoiding changes in molecular weight due to depolymerization of polyamic acid caused by heating.
When chemical imidization is performed, known compounds such as amines such as pyridine and β-picolinic acid, carbodiimides such as dicyclohexylcarbodiimide, and acid anhydrides such as acetic anhydride may be used as the chemical imidization agent. The acid anhydride is not limited to acetic anhydride, but may include, but is not limited to, propionic anhydride, n-butyric anhydride, benzoic anhydride, trifluoroacetic anhydride, and the like. In addition, a tertiary amine such as pyridine or β-picolinic acid may be used in combination. However, since these amines may adversely affect the properties if they remain in the cured film, the reaction solution in which the polyimide precursor is reacted to produce a polyimide resin may be purified by reprecipitation or the like, and the chemical imidization agent components other than polyimide may each be removed to 100 ppm or less of the total weight of the polyimide resin.

The organic solvent used in the reaction solution for chemically imidizing the polyimide precursor is not particularly limited as long as it can dissolve the polyimide precursor. For example, organic solvents containing nitrogen atoms such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, and 1,3-dimethyl-2-imidazolidinone; γ-butyrolactone, etc. can be used.

The molecular chain terminals of the polyimide resin may be carboxyl or amino terminals, and the terminals may be capped with a terminal capping agent. The terminal capping agent may be appropriately selected from known terminal capping agents, and examples of the terminal capping agent include monoamines, monocarboxylic acids, acid anhydrides, monoacid chloride compounds, and monoactive ester compounds.
When an acid anhydride is used for chemical imidization in preparing a polyimide resin, the acid anhydride may react with the amino terminals simultaneously with the chemical imidization. The polyimide resin used in the present invention may be one in which an acid anhydride has reacted with an amino terminal, and thus the polyimide resin has an amide bond at the terminal, or may have an acetamide group at the terminal.
In the resin composition of the present invention, from the viewpoint of improving adhesion to an uneven substrate and improving embeddability in unevenness by reacting the polyimide resin with an epoxy compound, 10% or more of the terminals of the molecular chain of the polyimide resin may have amide groups, 40% or more of the terminals may have amide groups, or 70% or more of the terminals may have amide groups.

A method for reprecipitating a reaction solution in which a polyimide precursor has been reacted to form a polyimide resin is generally to drop the reaction solution into a large amount of poor solvent while stirring it. In terms of easiness in reducing impurities, a method for reprecipitating a reaction solution is preferably to dilute the reaction solution in which a polyimide precursor has been reacted to form a polyimide resin to an appropriate concentration as necessary, and then gradually add a poor solvent for the polyimide resin to the reaction solution to precipitate the polyimide resin.
When the poor solvent is dropped to precipitate a polyimide resin, the solid content concentration of the reaction liquid (polyimide solution) is preferably 0.1 mass % or more and 30 mass % or less, and more preferably 1 mass % or more and 10 mass % or less, from the viewpoints of yield and efficient removal of impurities.
In order to adjust the solids concentration of the polyimide solution to a level suitable for precipitation of the polyimide resin, the polyimide solution may be appropriately diluted with a good solvent for the polyimide resin.
As a guideline, a good solvent for polyimide resin can be appropriately selected from solvents in which the solubility of polyimide resin is 20 g/100 g or more at 25° C.
The poor solvent for the polyimide resin can be appropriately selected from solvents in which the solubility of the polyimide resin at 25° C. is less than 20 g/100 g, as a guideline.

For example, an organic solvent that is a good solvent for polyimide resin is added to the reaction liquid obtained by reacting a polyimide precursor to a polyimide resin, and the reaction liquid is diluted by stirring until it becomes uniform. Next, an alcohol-based organic solvent such as t-butanol, methanol, ethanol, isopropyl alcohol, 2-butanol, cyclohexanol, or t-amyl alcohol is gradually added to precipitate the polyimide resin, obtaining a white slurry, which is then filtered to obtain the polyimide resin. The alcohol-based organic solvent may be a secondary or tertiary alcohol, in particular, because it provides excellent stability to the polyimide resin.

The polyimide resin obtained by reprecipitation as described above is preferably repeatedly washed with an organic solvent to remove residual solvent.
For example, the polyimide resin obtained by reprecipitation is washed in an organic solvent for washing, and then filtered. This washing process is repeated, and the polyimide resin is dried at 100° C. to 120° C. using a vacuum dryer to obtain the polyimide resin.
The organic solvent for cleaning is selected from among organic solvents that are highly compatible with the residual solvent contained in the polyimide resin obtained by reprecipitation, that are poor solvents for the polyimide resin, and that have a boiling point lower than the drying temperature of a vacuum dryer so that they can be completely volatilized by drying at 100°C to 120°C using a vacuum dryer.
For example, when the residual solvent is N,N-dimethylacetamide, N-methyl-2-pyrrolidone, etc., which are used in preparing the polyimide precursor, isopropyl alcohol, methanol, etc. are preferably used as the cleaning organic solvent. As the cleaning organic solvent, one or more kinds can be used.

The polyimide resin used in the present invention may have a weight average molecular weight of 50,000 or more, or 60,000 or more, and may be 100,000 or less, 90,000 or less, or 80,000 or less.
It is preferable that the weight average molecular weight of the polyimide resin is equal to or greater than the lower limit, since the tensile modulus of the cured film of the resin composition is easily improved, whereas it is equal to or less than the upper limit, since the increase in viscosity during synthesis of the polyimide resin, preparation of the resin composition, and coating film formation is suppressed, the thickness of the cured film of the resin composition can be increased, and the resin composition has excellent irregularity embedding properties.
The weight average molecular weight of the polyimide resin can be measured by gel permeation chromatography (GPC).

The polyimide resin of the present invention may have a tensile modulus and linear thermal expansion coefficient of a cured film similar to those described for the cured film of the resin composition described below. A cured film of the polyimide resin alone can be produced in the same manner as the cured film of the resin composition described below. The tensile modulus and linear thermal expansion coefficient of a cured film of the polyimide resin alone can be measured in the same manner as the tensile modulus and linear thermal expansion coefficient of a cured film of the resin composition described below.

2. Organic Solvent The organic solvent contained in the resin composition of the present invention is an organic solvent having a saturated vapor pressure of 0.5 kPa or less at 20° C. The organic solvent contained in the resin composition of the present invention is not particularly limited as long as it is capable of dissolving the polyimide resin, does not react with each component in the composition, and is capable of dissolving or dispersing these components, and for example, an aprotic polar solvent or the like can be used.
The organic solvent contained in the resin composition of the present invention may be appropriately selected from organic solvents in which the solubility of the polyimide resin is 5 g/100 g or more at 25° C. and the saturated vapor pressure at 20° C. is 0.5 kPa or less.
The saturated vapor pressure of an organic solvent at 20° C. can be confirmed by literature information such as Chemical Engineering Handbook, 6th Revised Edition (edited by the Society of Chemical Engineers) or by measurement using temperature-programmed gas chromatography in accordance with the Donovan method (New method for estimating vapor pressure by the use of gas chromatography: Journal of Chromatography A. 749 (1996) 123-129).

Examples of organic solvents having a saturated vapor pressure of 0.5 kPa or less at 20° C. include N,N-dimethylacetamide, N-methylpyrrolidone, benzyl acetate, ethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, γ-butyrolactone, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, and isophorone, and two or more of these may be mixed and used.
The organic solvent having a saturated vapor pressure of 0.5 kPa or less at 20° C. contained in the resin composition of the present invention may be at least one selected from the group consisting of N,N-dimethylacetamide, benzyl acetate, γ-butyrolactone, and isophorone, in terms of improving the unevenness embedding properties.
The organic solvent contained in the resin composition of the present invention may be an organic solvent having a saturated vapor pressure at 20° C. of 0.2 kPa or less, or may be an organic solvent having a saturated vapor pressure of 0.1 kPa or less at 20° C.

In the resin composition of the present invention, the content of the organic solvent may be appropriately set within a range that results in the viscosity described below, for example, depending on the purpose of use and processing conditions, and is not particularly limited. The content of the organic solvent is usually 70% by mass to 95% by mass, preferably 75% by mass to 90% by mass, and may be 87% by mass to 93% by mass, based on the total amount of the resin composition including the organic solvent.

3. Epoxy Compound The epoxy compound used in the resin composition of the present invention may be an epoxy compound having two or more epoxy groups in one molecule, or may be an epoxy compound having three or more epoxy groups in one molecule, from the viewpoint of the balance between the mechanical properties and the irregularity embedding property of the cured film of the resin composition.
Examples of epoxy compounds having three or more epoxy groups in one molecule include phenol novolac type epoxy resins, cresol novolac type epoxy resins, triphenylmethane type epoxy resins, dicyclopentadiene type epoxy resins, bisphenol A type epoxy resins, and tetramethylbisphenol F type epoxy resins.

The epoxy compound used in the resin composition of the present invention preferably contains an epoxy compound having three or more epoxy groups in one molecule and having a glycidyl amine moiety, from the standpoint of the balance between the mechanical properties and the irregularity embedding ability of the cured film of the resin composition, and from the standpoint of the ability to form a cured film of the resin composition with improved adhesion to inorganic compounds and metals.
An epoxy compound having three or more epoxy groups in one molecule and having a glycidyl amine moiety has, due to the amine moiety, excellent compatibility with the polyimide resin used in the present invention or excellent solubility in the organic solvent used in the present invention, and also has excellent reactivity when heated and stability when not heated (storage stability as a resin composition), and the epoxy group can react with an amino group, a carboxy group, an acetamide group, etc. at the terminal of the polyimide resin.

Examples of epoxy compounds having three or more epoxy groups in one molecule and having a glycidyl amine moiety include saturated or unsaturated aliphatic compounds, alicyclic compounds, aromatic compounds, heterocyclic compounds, or combinations thereof, which are derived from compounds having two or more amino groups, or one or more amino groups and one or more hydroxyl groups, have a glycidyl amine moiety, and may further have a glycidyl ether moiety.

Specific examples include epoxy compounds having a glycidylamine moiety derived from xylylenediamines such as metaxylylenediamine and paraxylylenediamine, epoxy compounds having a glycidylamine moiety derived from 1,3-bis(aminomethyl)cyclohexane, epoxy compounds having a glycidylamine moiety derived from diaminodiphenylmethane, epoxy compounds having a glycidylamine moiety and a glycidyl ether moiety derived from paraaminophenol, and epoxy compounds having a glycidylamine moiety and a glycidyl ether moiety derived from 4-amino-3-methylphenol.

More specific examples include N,N,N',N'-tetraglycidylmeta-xylylenediamine, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, N,N,N',N'-tetraglycidyl-4,4-(4-aminophenyl)-p-diisopropylbenzene, 1,1,2,2-(tetraglycidyloxyphenyl)ethane, 1,1,2,2-tetrabis(hydroxyphenyl)ethane tetraglycidyl ether, tetraglycidyl-1,3-bisaminomethylcyclohexane, N-[2-methyl-4-(oxiranylmethoxy)phenyl]-N-(oxiranylmethyl)oxiranemethanamine, and the like.
Among them, an epoxy compound containing a skeleton structure represented by the following chemical formula (I) in the molecule is more preferable.

As the epoxy compound having three or more epoxy groups in one molecule and having a glycidyl amine moiety used in the present invention, from the viewpoints of compatibility and solubility, it is preferable to contain one or more selected from the group consisting of an epoxy compound having a glycidyl amine moiety derived from metaxylylenediamine, an epoxy compound having a glycidyl amine moiety derived from diaminodiphenylmethane, and an epoxy compound having a glycidyl amine moiety and a glycidyl ether moiety derived from 4-amino-3-methylphenol, and it is more preferable to contain one or more selected from the group consisting of an epoxy compound having a glycidyl amine moiety derived from metaxylylenediamine, and an epoxy compound having a glycidyl amine moiety and a glycidyl ether moiety derived from 4-amino-3-methylphenol.

The epoxy compounds used in the present invention can be produced by conventionally known production methods, and are obtained by reacting various alcohols, phenols, and amines with epihalohydrin. For example, an epoxy compound having a glycidylamine moiety derived from metaxylylenediamine can be obtained by adding epichlorohydrin to metaxylylenediamine.

As the epoxy compound having three or more epoxy groups in one molecule and having a glycidylamine moiety used in the present invention, from the viewpoints of compatibility and solubility, N,N,N',N'-tetraglycidylmeta-xylylenediamine represented by the following chemical formula (Ia), N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane represented by the following chemical formula (Ib), and N-[2-methyl-4-(oxiranylmethoxy)phenyl]-N-(oxiranylmethoxy)phenyl represented by the following chemical formula (Ic) are particularly preferred. and N-[2-methyl-4-(oxiranylmethoxy)phenyl]-N-(oxiranylmethyl)oxiranemethanamine represented by the following chemical formula (Ia):
As the epoxy compound used in the present invention, a commercially available product may be appropriately selected and used. For example, polyepoxy resin of Maxive M-100 (manufactured by Mitsubishi Gas Chemical Co., Ltd.), Sumiepoxy ELM-434 series, Sumiepoxy ELM-100 series (all manufactured by Sumitomo Chemical Co., Ltd.), etc. can be used.

The epoxy compounds used in the present invention may be used alone or in combination of two or more kinds.
The total content of the epoxy compounds having three or more epoxy groups in one molecule and having a glycidyl amine moiety may be 70% by mass or more, 90% by mass or more, or may be 100% by mass, based on the total amount of the epoxy compounds.

The content of the epoxy compound used in the present invention may be appropriately selected based on the desired balance between physical properties such as mechanical properties and the ability to embed unevenness, and is not particularly limited. For example, the content may be 1 to 30 parts by mass, and preferably 3 to 25 parts by mass, per 100 parts by mass of the polyimide resin.

4. Other Components The resin composition of the present invention may further contain other components in addition to the above-mentioned components, so long as the effects of the present invention are not impaired.
Examples of other components include photosensitive components, crosslinking agents, antioxidants, surfactants, leveling agents, inorganic or organic fine particles, and rust inhibitors. These other components can be appropriately selected from known components. Note that each of these other components may not be contained.
In order to further improve adhesion, a silane coupling agent may be contained. As the silane coupling agent, a known silane coupling agent can be appropriately selected and used.

The silane coupling agent used in the resin composition of the present invention may be a compound represented by the following general formula (A) in order to further improve adhesion.

（式（Ａ）中、Ｒ^ａは、グリシジル基、（メタ）アクリロイル基、酸無水物基、ヒドロキシ基、トリアジン基、及びアミノ基からなる群から選択される少なくとも１種を含む１価の基を表し、Ｒ^ｂ及びＲ^ｃはそれぞれ独立に、炭素数１～５のアルキル基であり、ｎは１～１０の整数であり、ｍは１～３の整数である。）

(In formula (A), R ^a represents a monovalent group containing at least one selected from the group consisting of a glycidyl group, a (meth)acryloyl group, an acid anhydride group, a hydroxy group, a triazine group, and an amino group; R ^b and R ^c each independently represent an alkyl group having 1 to 5 carbon atoms; n represents an integer of 1 to 10; and m represents an integer of 1 to 3.)

R ^b and R ^c may each independently be an alkyl group having 1 to 3 carbon atoms, and may be a methyl group or an ethyl group.
n may be 1-5.

Examples of compounds represented by the following general formula (A) include hydroxymethyltrimethoxysilane, hydroxymethyltriethoxysilane, 2-hydroxyethyltrimethoxysilane, 2-hydroxyethyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, 3-hydroxypropyltriethoxysilane, 4-hydroxybutyltrimethoxysilane, 4-hydroxybutyltriethoxysilane, glycidoxymethyltrimethoxysilane, glycidoxymethyltriethoxysilane, 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 4-glycidoxybutyltrimethoxysilane, 4-glycidoxybutyltriethoxysilane, bis(2-hydroxymethyl)-3-aminopropyltriethoxysilane, bis(2 2-(hydroxymethyl)-3-aminopropyltrimethoxysilane, bis(2-glycidoxymethyl)-3-aminopropyltriethoxysilane, bis(2-hydroxymethyl)-3-aminopropyltrimethoxysilane, ureidomethyltrimethoxysilane, ureidomethyltriethoxysilane, 2-ureidoethyltrimethoxysilane, 2-ureidoethyltriethoxysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane, 4-ureidobutyltrimethoxysilane, 4-ureidobutyltriethoxysilane, 3-trimethoxysilylpropylsuccinic anhydride, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, and the compound represented by the following formula (a-1). The compound represented by the following formula (a-1) can be prepared by referring to JP-A-62-100462.

（式（ａ－１）中、Ｒ^ｄは、－ＣＨ_２ＣＨ_２－Ｓ－、又は、－ＣＨ_２ＣＨ_２－ＮＨ－を表し、Ｒ^ｂ及びＲ^ｃはそれぞれ独立に、炭素数１～５のアルキル基であり、ｎは１～１０の整数であり、ｍは１～３の整数である。）

(In formula (a-1), R ^d represents —CH ₂ CH ₂ —S— or —CH ₂ CH ₂ —NH—, R ^b and R ^c each independently represent an alkyl group having 1 to 5 carbon atoms, n represents an integer of 1 to 10, and m represents an integer of 1 to 3.)

As the silane coupling agent used in the resin composition of the present invention, in the compound represented by the general formula (A), R ^a may represent a monovalent group containing at least one selected from the group consisting of a glycidyl group, a triazine group, and an amino group, or may represent a monovalent group containing at least one selected from the group consisting of a glycidyl group and a triazine group, and may be a compound represented by the formula (a-1).

The silane coupling agents may be used alone or in combination of two or more.
The content of the silane coupling agent may be appropriately selected depending on the balance between the desired adhesion and the desired physical properties, and is not particularly limited. For example, the content may be 0.1 parts by mass to 10 parts by mass, and preferably 0.5 parts by mass to 5 parts by mass, relative to 100 parts by mass of the polyimide resin.

The resin composition of the present invention can be prepared by dissolving the polyimide resin and the epoxy compound in the organic solvent, and further dissolving or dispersing other components as required.
The content of the polyimide resin in the resin composition may be appropriately selected depending on the application, etc., and is not particularly limited.
The resin composition used for the cured film of the resin composition of the present invention described later may have a polyimide resin content of 5 mass % or more, 10 mass % or more, 30 mass % or less, or 25 mass % or less, relative to the total amount of the resin composition.

The viscosity of the resin composition of the present invention may be appropriately selected depending on the application, etc., and is not particularly limited.
The resin composition of the present invention may have a viscosity of 3,000 mPa·s or more, or 4,000 mPa·s or more, or may have a viscosity of 7,000 mPa·s or less, or 6,000 mPa·s or less, at 25° C. when the solid content other than the organic solvent is 7 to 13 mass %, from the viewpoints of being capable of increasing the film thickness and of being excellent in embedding properties of the unevenness.
The viscosity of the resin composition can be measured at 25° C. by the method described in JIS K7117-1 using a single cylinder type rotational viscometer (for example, TVB-10 type viscometer manufactured by Toki Sangyo Co., Ltd.).

II. Cured Film of Resin Composition The present invention provides a cured film obtained by curing the resin composition of the present invention.
The cured film of the resin composition according to the present invention contains the polyimide resin, the epoxy compound, solid contents of other components, and reaction products thereof.

The cured film of the resin composition of the present invention has a tensile modulus of elasticity of 4.5 GPa or more at 25 ° C., may be 4.6 GPa or more, or may be 5.0 GPa or more. In this way, a high tensile modulus at 25 ° C. (room temperature) is advantageous in terms of physical stability of the package when used in a new semiconductor package of a type in which multiple semiconductor packages are vertically integrated. On the other hand, the tensile modulus may be 10.0 GPa or less from the viewpoint of concerns about brittle fracture.
The tensile test can be performed in accordance with JIS K7127 using a tensile tester (e.g., Shimadzu Corporation: Autograph AG-X 1N, load cell: SBL-1KN) by cutting a test piece of 10 mm width x 150 mm length from the cured film of the resin composition, at 25°C, at a stretching speed of 50 mm/min, and with a gripper distance of 100 mm. The tensile modulus can be determined from the initial gradient of the stress-strain curve. The cured film of the resin composition when performing the tensile test may have a thickness of 40 μm ± 5 μm.

The linear thermal expansion coefficient of the cured film of the resin composition of the present invention may be 40 ppm or less, or 36 ppm or less, from the viewpoint of dimensional stability when used as a semiconductor packaging material, etc. Here, the linear thermal expansion coefficient in the present invention can be calculated from a TMA curve obtained by heating the film from 30°C to 400°C at a heating rate of 10°C/min with a load of 9 g using a thermomechanical analyzer (for example, a thermomechanical analyzer (TMA-60), manufactured by Shimadzu Corporation). The linear thermal expansion coefficient is calculated as the average value between 100 and 150°C.

The thickness of the cured film of the resin composition of the present invention may be appropriately selected depending on the application, and is not particularly limited, but may be 1 μm or more, 20 μm or more, 30 μm or more, or 35 μm or more. On the other hand, it may be 100 μm or less, 70 μm or less, or 55 μm or less.

The cured film of the resin composition of the present invention may also be subjected to a surface treatment such as saponification treatment, glow discharge treatment, corona discharge treatment, ultraviolet treatment, or flame treatment.

[Method for producing a cured film of a resin composition]
The method for producing a cured film of the resin composition of the present invention is not particularly limited as long as it is a method that can produce a cured film of the resin composition of the present invention.
The method for producing a cured film of the resin composition of the present invention includes the following steps:
A step of applying the resin composition onto a substrate and drying it to form a coating film;
The method for producing a cured film of a resin composition includes a step of heating the coating film to form a cured film.

In the step of forming the coating film, the substrate to be used is not particularly limited.For example, the substrate may be a glass substrate, a semiconductor substrate such as a Si substrate (silicon wafer), a metal oxide insulator substrate such as a _TiO2 substrate or a _SiO2 substrate, a silicon nitride substrate, a copper substrate, a copper alloy substrate, a composite substrate formed by laminating a resin film such as a polyimide film on these substrates, or a concave-convex substrate having a structure such as wiring on these substrates.
The resin composition of the present invention has excellent irregularity-filling properties and can therefore be suitably used for substrates having irregularities on the surface, such as an irregular substrate having wiring or other structures thereon.
In addition, since the resin composition of the present invention contains a ring-closed polyimide instead of a polyimide precursor, it can be cured at a low temperature, and therefore a cured film of the resin composition can be suitably produced even on a mold resin having low heat resistance or a substrate equipped with an IC chip.

The coating means is not particularly limited as long as it is a method that can coat the film at the desired thickness, and known methods such as a spin coater, die coater, comma coater, roll coater, gravure coater, curtain coater, spray coater, and lip coater can be used.

After the resin composition is applied to the substrate, it is dried to form a coating film. The drying temperature is less than 150°C, preferably 30°C or higher and 140°C or lower.

The drying time may be adjusted as appropriate depending on the thickness of the resin composition coating, the type of solvent, the drying temperature, etc., but is usually 5 to 60 minutes, preferably 10 to 40 minutes. If the upper limit is exceeded, this is not preferable in terms of the efficiency of producing a cured film of the resin composition. On the other hand, if the drying time is below the lower limit, the solvent will not be dried sufficiently and a large amount of solvent will remain in the coating, and the remaining solvent will rapidly volatilize during heating in the subsequent cured film formation process, which may affect the appearance of the cured film of the resulting resin composition.

The method for drying the solvent is not particularly limited as long as it is possible to dry the solvent at the above-mentioned temperature. For example, an oven, a drying furnace, a hot plate, infrared heating, or the like can be used.
The atmosphere during drying of the solvent may be either air or an inert gas atmosphere.

The coating film is heated to form a cured film.
The temperature to which the coating film is heated may be 150° C. or higher and 240° C. or lower, 170° C. or higher and 235° C. or lower, or 200° C. or higher and 230° C. or lower, from the viewpoints of accelerating the curing reaction and of the heat resistance of other semiconductor packaging materials such as encapsulants.
The heating means used for forming the cured film may be the same as that used for drying.
The coating may be heated in air or in an inert gas atmosphere.

The heating time can be adjusted appropriately depending on the thickness of the coating, but is usually 10 minutes to 2 hours, preferably 30 minutes to 1 hour.

In addition, when the resin composition contains a photosensitive component, a patterned coating film may be formed by performing patterned exposure after forming the coating film and appropriately developing the coating film, and a patterned cured film may be formed by heating the patterned coating film.

The use of the cured film of the resin composition of the present invention is not particularly limited, but since it has excellent mechanical strength and excellent unevenness embedding properties, it can be suitably used, for example, as various resin films in semiconductor electronic components or semiconductor devices. Specifically, it can be suitably used, for example, as a passivation film for semiconductor devices, a surface protection film for semiconductor elements, an interlayer insulating film, an interlayer insulating film for multilayer wiring for high-density mounting, an insulating film for organic electroluminescent elements, and the like. In addition, the cured film of the resin composition of the present invention can also be applied to components for image display devices such as liquid crystal display devices and organic EL display devices, components for touch panels, flexible printed circuit boards, components for solar cell panels such as surface protection films and substrate materials, components for optical waveguides, and other semiconductor-related components.

III. Insulating Film, Protective Film, and Electronic Component The present invention provides an insulating film produced using the cured film of the present invention.
The present invention also provides a protective film produced using the cured film of the present invention.
The present invention also provides an electronic component including the insulating film according to the present invention or the protective film according to the present invention.

The insulating film or protective film may be a film that combines the functions of an insulating film and a protective film, and can be used, for example, as an interlayer insulating film for a redistribution layer, a passivation film, a buffer coat film, a surface protective film, etc.

By using one or more selected from the group consisting of the above passivation films, buffer coat films, interlayer insulating films, and surface protection films, it is possible to manufacture highly reliable electronic components such as semiconductor devices, multilayer wiring boards, and various electronic devices.

An example of a manufacturing process for a semiconductor device, which is an electronic component of the present invention, will be described with reference to the drawings.
FIG. 1 is a manufacturing process diagram of a semiconductor device having a multi-layer wiring structure, which is an electronic component according to an embodiment of the present invention.
1A, a semiconductor substrate 1 such as a Si substrate having circuit elements is covered with a protective film 2 such as a silicon oxide film except for a predetermined portion of the circuit elements, and a first conductor layer 3 is formed on the exposed circuit elements. Then, a cured film of a resin composition is formed on the semiconductor substrate 1 using the resin composition of the present invention, and an interlayer insulating film 4 is formed.

Next, as shown in FIG. 1B, a photosensitive resin layer 5 is formed on the interlayer insulating film 4, and a window 6A is provided by known photolithography techniques so that a predetermined portion of the interlayer insulating film 4 is exposed.

As shown in FIG. 1C, the interlayer insulating film 4 from which the window 6A is exposed is selectively etched by a suitable known method to provide a window 6B.
Next, the photosensitive resin layer 5 is removed using an etching solution that will corrode the photosensitive resin layer 5 without corroding the first conductor layer 3 exposed through the window 6B.

As shown in FIG. 1D, a second conductor layer 7 is formed by using a known photolithography technique, and is electrically connected to the first conductor layer 3.
When forming a multi-layer wiring structure having three or more layers, the above steps can be repeated to form each layer.

1(E), the resin composition of the present invention is used to form a cured film of the resin composition, and windows 6C are opened by a laser or the like to form a surface protective film 8. Alternatively, when the resin composition of the present invention contains a photosensitive component and is a photosensitive composition, a coating film of the resin composition may be formed, windows 6C are opened by pattern exposure, and a cured film is formed to form the surface protective film 8. The surface protective film 8 protects the second conductor layer 7 from external stress, α-rays, and the like, and the resulting semiconductor device has excellent reliability.
In the above example, the interlayer insulating film may be formed using the resin composition of the present invention.

The electronic component of the present invention may be an electronic component including an IC chip, a molding resin surrounding at least the IC chip, and a wiring layer including an insulating film and wiring produced using the cured film of the present invention.
As described above, the resin composition of the present invention has low-temperature curing properties and excellent unevenness embedding properties, and the cured film of the resin composition has excellent mechanical strength, so that the cured film of the present invention can be produced on a substrate including an IC chip having low heat resistance, at least a molded resin surrounding the IC chip, and further wiring, and an electronic component including an IC chip, at least a molded resin surrounding the IC chip, and a wiring layer including an insulating film and wiring produced using the cured film of the present invention can be suitably produced. In the electronic component of the present invention, the wiring layer may be a rewiring layer.

The electronic component of the present invention may be, for example, a semiconductor device having an insulating film made of a cured film of the resin composition of the present invention as shown in FIG. 2. FIG. 2 is an enlarged cross-sectional view of a pad portion of a semiconductor device having an insulating film of the present invention, and has a structure called a fan-out wafer level package (FOWLP). As shown in FIG. 2, an IC chip 11 having metal wiring 12 is sealed with a molded resin 13. An insulating film 14 is formed as a cured film of the resin composition of the present invention over the molded resin 13 and the IC chip 11, and further, metal wiring 15 and metal wiring 16 are formed. Furthermore, a barrier metal 18 and a solder bump 20 are formed in an opening of an insulating film 17 formed as a cured film of the resin composition of the present invention on the insulating film 14 and the metal wirings 15 and 16.

The IC (Integrated Circuit) chip is not particularly limited, and any known IC chip can be appropriately selected and used.

Since the resin composition of the present invention is curable at low temperature, it is possible to use a molding resin having a relatively low heat resistance as the molding resin, and the molding resin may be, for example, a cured product of an epoxy resin composition.
The epoxy resin composition used as the molding resin is a resin composition containing an epoxy compound, and an appropriate epoxy resin material that has been used in conventional molding resins can be selected and used.

[Evaluation method]
Unless otherwise specified, measurements or evaluations were performed at 25° C. In addition, room temperature refers to 25° C.
The film specimens were cut near the center of the film.

<Confirmation of imidization rate of polyimide resin ( ¹ H NMR)>
Approximately 10 mg of polyimide resin was dissolved in 0.75 mL of deuterated dimethyl sulfoxide containing 0.03 vol% tetramethylsilane (TMS), and a Fourier transform nuclear magnetic resonance apparatus (AVANCE400, manufactured by Bruker) was used to perform measurement under the condition of 256 accumulations for ¹ H nuclei. The chemical shifts were based on TMS (0 ppm), and signals derived from carboxy protons of polyamic acid (near 13 ppm) and amide protons (near 11 ppm) were confirmed.

<Weight average molecular weight of polyimide resin>
The polyimide resin was dissolved in N-methylpyrrolidone (NMP) at a concentration of 0.5% by mass, and the solution was filtered through a syringe filter (pore size: 0.45 μm). As a developing solvent, a 10 mmol% LiBr-NMP solution was used, and a GPC apparatus (Tosoh HLC-8120, detector: refractive index differential (RID) detector, column used: SHODEX GPC LF-804) was used, and the sample was injected at a volume of 50 μL, a solvent flow rate of 0.4 mL/min, a column temperature of 37 ° C., and a detector temperature of 37 ° C. The weight average molecular weight of the polyimide resin was measured based on a polystyrene standard sample (weight average molecular weight: 364,700, 204,000, 103,500, 44,360,27,500, 13,030, 6,300, 3,070) of the same concentration as the sample. The converted value was determined based on standard polystyrene. The elution time was compared with a calibration curve to determine the weight average molecular weight.

<Measurement of Viscosity of Resin Composition>
The viscosity of the resin composition was measured at 25° C. using 0.8 mL of the resin composition with an E-type viscometer (for example, TVE-22HT, manufactured by Toki Sangyo Co., Ltd.) according to the method described in JIS K7117-2.

<Preparation of cured film>
The resin composition was spin-coated on a glass substrate (OA-11 (alkali-free glass substrate) manufactured by Nippon Electric Glass Co., Ltd.) on which a polyimide film (UPILEX (registered trademark) 125S manufactured by UBE Corporation, [5,5'-biisobenzofuran]-1,1',3,3'-tetraone-1,4-phenylenediamine polycondensate) was attached. The spin-coating conditions were adjusted so that the thickness of the cured film of the resin composition finally obtained was 40 μm ± 5 μm. After spin-coating the resin composition, the substrate was heated on a hot plate at 40°C for 8 minutes, then at 80°C for 8 minutes, and then at 130°C for 8 minutes to dry the solvent. After drying, the substrate was placed in an oven and heated in the atmosphere at 200°C for 1 hour, allowed to cool to 25°C, and the cured film of the resin composition was peeled off from the substrate to prepare a cured film.
A cured film of polyimide resin alone (PI cured film) was prepared in the same manner as above, using a γ-butyrolactone solution of polyimide resin with a concentration of 7 to 13% by mass instead of the resin composition.

<Method for measuring thickness of cured film>
The film thickness of a test piece of the cured film of the resin composition cut into a size of 100 mm x 100 mm was measured at a total of five points, namely, the four corners and the center, using a digital linear gauge (manufactured by Ozaki Seisakusho Co., Ltd., model PDN12 digital gauge), and the average of the measured values was regarded as the film thickness of the cured film of the resin composition.

<Evaluation of mechanical properties of cured film (tensile test): Tensile modulus>
The tensile test was carried out in accordance with JIS K7127 using test pieces of the cured film of the resin composition or the cured polyimide film cut to a size of 10 mm wide x 150 mm long, with a tensile tester (e.g., Shimadzu Corporation: Autograph AG-X 1N, load cell: SBL-1KN) at 25°C, a stretching speed of 50 mm/min, and a gripping distance of 100 mm.
The tensile modulus was determined from the initial slope of the stress-strain curve.

<Evaluation of Thermal Properties of Cured Film: Coefficient of Linear Thermal Expansion (CTE)>
A test piece of the cured film of the resin composition cut into a size of 5 mm x 10 mm was used to obtain a TMA curve with a thermomechanical analyzer (TMA-60, manufactured by Shimadzu Corporation) when the temperature was raised from 30°C to 400°C at a rate of 10°C/min under a load of 9 g.
The linear thermal expansion coefficient was determined as the average value between 100 and 150°C.

<Evaluation of unevenness filling ability>
A test substrate (φ8inc insulating resin test substrate manufactured by Shinryo Corporation was used. Copper wiring height: about 20 μm, copper wiring width: about 15 μm, wiring interval: about 110 μm) on which a test pattern of copper wiring was drawn was cut into a 40 mm × 40 mm square on an 8-inch silicon wafer having a thickness of about 700 μm, and the resin composition was spin-coated on this uneven substrate so that the thickness of the cured film of the resin composition finally obtained was 40 μm ± 5 μm in the part (recess) where no copper wiring was present. After spin-coating the resin composition, the substrate was heated on a hot plate at 40 ° C. for 8 minutes, then heated at 80 ° C. for 8 minutes, and then heated at 130 ° C. for 8 minutes to dry the solvent. After drying, the substrate was placed in an oven, heated at 200 ° C. in the atmosphere for 1 hour, and allowed to cool to 25 ° C. to prepare an unevenness embedding evaluation substrate.
A cross section was formed by FIB processing for the copper wiring portion of the substrate for evaluating unevenness embeddability, and the cross section was observed with an SEM (Helios G4 PFIB manufactured by Thermo Scientific Corp.) to confirm whether the cured film was embedded without gaps in the concave portions on both sides of the copper wiring (convex portions) up to the vicinity of the substrate interface, thereby evaluating unevenness embeddability.
(Evaluation criteria)
◯: The cured film is embedded in the recessed portion up to the substrate interface with no gaps.
×: The cured film is not embedded in the recessed portion all the way to the substrate interface without leaving any gaps.

Example 1
(1) Synthesis and Evaluation of Polyimide Resin Under a nitrogen atmosphere, dehydrated N,N-dimethylacetamide (DMAc) (300 g), 2,2'-bis(trifluoromethyl)benzidine (TFMB, manufactured by Seika Corporation) (15.00 g, 46.9 mmol), and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (DABPAF, manufactured by Seika Corporation) (7.35 g, 20.1 mmol) were placed in a 500 mL separable flask and stirred at room temperature to dissolve TFMB and DABPAF. To the above solution, TMPBP-TME (manufactured by Honshu Chemical Industry Co., Ltd.) (23.19 g, 37.5 mmol) represented by the above chemical formula (1-1), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) (3.02 g, 9.4 mmol), and pyromellitic anhydride (PMDA) (4.38 g, 20.1 mmol) were added in several portions, and the mixture was stirred at room temperature for 15 hours to obtain a polyimide precursor solution (solid content: approximately 15% by mass) in which the polyimide precursor (polyamic acid) was dissolved.
A mixed solution of 20.50 g of acetic anhydride and 0.79 g of pyridine was slowly added dropwise to the obtained polyimide precursor solution at room temperature, and after the dropwise addition was completed, the mixture was stirred for an additional 15 hours to obtain a polyimide solution (solid content: approximately 15% by mass).
The resulting polyimide solution was diluted with ethyl acetate to a solid content of about 5% by mass, and then a large amount of isopropyl alcohol was added with vigorous stirring to precipitate the polyimide resin. The resulting precipitate was filtered, washed with isopropyl alcohol, and then dried at 110° C. for 8 hours in a vacuum dryer to obtain a polyimide resin.
The obtained polyimide resin 1 was subjected to ¹ H NMR measurement, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that the imidization had progressed completely.
The weight average molecular weight of the obtained polyimide resin 1 was measured by the above-mentioned method.

(2) Preparation and Evaluation of Resin Composition A solvent (isophorone, saturated vapor pressure at 20°C is 0.04 kPa) was added to the obtained polyimide resin, and the polyimide resin was dissolved by stirring at room temperature to prepare a homogeneous solution with a polyimide concentration of 10% by mass. To this solution, 3 parts by mass of an epoxy compound having four epoxy groups in one molecule and having a glycidylamine moiety (Maxive M-100 (MXV-M100), N,N,N',N'-tetraglycidyl metaxylylenediamine, manufactured by Mitsubishi Gas Chemical Company) was added per 100 parts by mass of the polyimide resin, and the mixture was stirred and mixed. This solution was pressure filtered using a 400-mesh wire screen to obtain resin composition 1.
The viscosity of the resulting resin composition was measured by the above-mentioned method.

(3) Production and Evaluation of Cured Film of Resin Composition Using the obtained resin composition, a cured film of the resin composition was produced by the method described above.
The tensile modulus and linear thermal expansion coefficient of the resulting cured film were measured by the above-mentioned methods.
Using the obtained resin composition, a substrate for evaluating unevenness embeddability was produced and evaluated by the above-mentioned method.
The evaluation results obtained are shown in Table 1.

Example 2
Resin composition 2 was prepared in the same manner as in Example 1, except that in the preparation of the resin composition of Example 1, γ-butyrolactone (saturated vapor pressure at 20° C.: 0.06 kPa) was used as the solvent instead of isophorone.
Using the resin composition 2, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 1.

Example 3
Resin composition 3 was prepared in the same manner as in Example 1, except that in the preparation of the resin composition of Example 1, benzyl acetate (saturated vapor pressure at 20° C.: 0.19 kPa) was used as the solvent instead of isophorone.
Using the resin composition 3, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 1.

Example 4
Resin composition 4 was prepared in the same manner as in Example 1, except that in the preparation of the resin composition of Example 1, N,N-dimethylacetamide (saturated vapor pressure at 20°C: 0.33 kPa) was used as the solvent instead of isophorone.
Using this resin composition 4, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 1.

(Comparative Example 1)
Comparative resin composition 1 was prepared in the same manner as in Example 1, except that in the preparation of the resin composition of Example 1, cyclohexanone (saturated vapor pressure at 20° C.: 0.58 kPa) was used as the solvent instead of isophorone.
Using the comparative resin composition 1, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 1.

(Comparative Example 2)
Comparative resin composition 2 was prepared in the same manner as in Example 1, except that in the preparation of the resin composition of Example 1, cyclopentanone (saturated vapor pressure at 20° C.: 1.52 kPa) was used as the solvent instead of isophorone.
Using the comparative resin composition 2, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 1.

(Comparative Example 3)
Comparative resin composition 3 was prepared in the same manner as in Example 1, except that in the preparation of the resin composition of Example 1, tetrahydrofuran (saturated vapor pressure at 20° C.: 19.33 kPa) was used as the solvent instead of isophorone.
Using the comparative resin composition 3, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 1.

(Comparative Example 4)
In the synthesis of the polyimide resin of Example 1, TFMB was not used as the diamine component, but DABPAF (23.09 g, 63.0 mmol) was used, the molar ratio was changed to TMPBP-TME (21.84 g, 35.3 mmol), BTDA (6.09 g, 18.9 mmol), and PMDA (1.92 g, 8.82 mmol) as the tetracarboxylic acid dianhydride component, and DMAc was changed to 319 g. Except for this, a polyimide resin was synthesized in the same manner as in Example 1 to obtain polyimide resin C1. ¹ H NMR measurement was performed on the obtained polyimide resin C1, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that imidization had progressed completely.
Comparative resin composition 4 was prepared in the same manner as in Comparative Example 2, except that polyimide resin C1 was used instead of polyimide resin 1 in Comparative Example 2, and cyclopentanone was used as the solvent.
Using the comparative resin composition 4, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 1.

As shown in Comparative Example 4 in Table 1, when the tensile modulus of elasticity of the cured film is low, such as 3.8 GPa, the unevenness filling property is good even if a solvent with a high saturated vapor pressure is used as the organic solvent.
However, as shown in Comparative Examples 1 to 3, in a resin composition that produces a cured film with a tensile modulus of elasticity of 4.5 GPa or more, if a solvent with a high saturated vapor pressure is used as the organic solvent, the unevenness is not filled and the unevenness filling ability is deteriorated.
In contrast, as shown in Examples 1 to 4, it was revealed that in a resin composition that produces a cured film with a tensile modulus of elasticity of 4.5 GPa or more, when an organic solvent having a saturated vapor pressure of 0.5 kPa or less at 20°C is used as the solvent for the resin composition, the unevenness embedding property is improved.
It was revealed that the resin compositions of Examples 1 to 4 of the present invention are resin compositions that are capable of forming a cured film having a high tensile modulus of elasticity of 4.5 GPa or more by heating at a low temperature of 200° C. or less, and have excellent irregularity embedding properties. The cured films of the resin compositions of Examples 1 to 4 of the present invention also had a low linear thermal expansion coefficient.

Example 5
Resin composition 5 was prepared in the same manner as in Example 2, except that in the resin composition of Example 2 (organic solvent: γ-butyrolactone), 1 part by mass of an epoxy compound was added instead of 3 parts by mass per 100 parts by mass of the polyimide resin.
Using the resin composition 5, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 2 together with the results of the resin composition of Example 2.

(Example 6)
Resin composition 6 was prepared in the same manner as in Example 2, except that in the resin composition of Example 2 (organic solvent: γ-butyrolactone), 7 parts by mass of an epoxy compound was added instead of 3 parts by mass per 100 parts by mass of the polyimide resin.
Using the resin composition 6, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 2.

(Example 7)
A polyimide resin was synthesized in the same manner as in Example 1, except that TFMB (21.43 g, 66.9 mmol) was used instead of TFMB and DABPAF, and 295 g of DMAc was used, to obtain polyimide resin 2. The obtained polyimide resin 2 was subjected to ¹ H NMR measurement, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that imidization had progressed completely.
Resin composition 7 was prepared in the same manner as in Example 2, except that polyimide resin 2 was used instead of polyimide resin 1 in the resin composition of Example 2.
Using the resin composition 7, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 2.

(Example 8)
In the synthesis of the polyimide resin of Example 1, TFMB (15.00 g, 46.9 mmol) and DABPAF (7.35 g, 20.1 mmol) were used instead of TFMB (17.15 g, 53.5 mmol) and DABPAF (4.90 g, 13.4 mmol), and 298 g of DMAc were used, but the procedure was the same as in Example 1 to synthesize a polyimide resin, thereby obtaining a polyimide resin 3. The obtained polyimide resin 3 was subjected to ¹ H NMR measurement, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that the imidization had progressed completely.
Resin composition 8 was prepared in the same manner as in Example 2, except that polyimide resin 3 was used instead of polyimide resin 1 in the resin composition of Example 2.
Using the resin composition 8, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 2.

Example 9
In the synthesis of the polyimide resin of Example 1, TFMB (15.00 g, 46.9 mmol) and DABPAF (7.35 g, 20.1 mmol) were used instead of TFMB (12.86 g, 40.2 mmol) and DABPAF (9.81 g, 26.8 mmol), and 302 g of DMAc were used, but the procedure was the same as in Example 1 to synthesize a polyimide resin, thereby obtaining polyimide resin 4. The obtained polyimide resin 4 was subjected to ¹ H NMR measurement, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that imidization had progressed completely.
Resin composition 9 was prepared in the same manner as in Example 2, except that polyimide resin 4 was used instead of polyimide resin 1 in the resin composition of Example 2.
Using the resin composition 9, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 2.

Example 10
In the synthesis of the polyimide resin of Example 1, instead of using TMPBP-TME (23.19 g, 37.5 mmol), PMDA (4.38 g, 20.1 mmol), and BTDA (3.02 g, 9.4 mmol), TMPBP-TME (23.19 g, 37.5 mmol), PMDA (2.04 g, 9.40 mmol), and BTDA (6.47 g, 20.1 mmol) were used, and DMAc was changed to 306 g, except that a polyimide resin was synthesized in the same manner as in Example 1 to obtain polyimide resin 5. The obtained polyimide resin 5 was subjected to ¹ H NMR measurement, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that imidization had progressed completely.
Resin composition 10 was prepared in the same manner as in Example 2, except that polyimide resin 5 was used instead of polyimide resin 1 in the resin composition of Example 2.
Using the resin composition 10, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 2.

(Example 11)
In the synthesis of the polyimide resin of Example 1, a polyimide resin was synthesized in the same manner as in Example 1, except that, instead of using TMPBP-TME (23.19 g, 37.5 mmol), PMDA (4.38 g, 20.1 mmol), and BTDA (3.02 g, 9.4 mmol), as well as TFMB (15.00 g, 46.9 mmol), and DABPAF (7.35 g, 20.1 mmol), TMPBP-TME (32.46 g, 52.5 mmol), PMDA (1.27 g, 5.80 mmol), as well as TFMB (14.94 g, 46.4 mmol), and DABPAF (4.27 g, 11.7 mmol), and 344 g of DMAc was used. Polyimide resin 6 was obtained. The obtained polyimide resin 6 was subjected to ¹ H NMR measurement, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that the imidization had progressed completely.
Resin composition 11 was prepared in the same manner as in Example 2, except that polyimide resin 6 was used instead of polyimide resin 1 in the resin composition of Example 2.
Using the resin composition 11, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 2.

Example 12
In the synthesis of the polyimide resin of Example 1, a polyimide resin was synthesized in the same manner as in Example 1, except that, instead of using TMPBP-TME (23.19 g, 37.5 mmol), PMDA (4.38 g, 20.1 mmol), and BTDA (3.02 g, 9.4 mmol), as well as TFMB (15.00 g, 46.9 mmol), and DABPAF (7.35 g, 20.1 mmol), TMPBP-TME (32.30 g, 52.2 mmol), PMDA (1.27 g, 5.8 mmol), as well as TFMB (13.00 g, 40.6 mmol), and DABPAF (6.37 g, 17.4 mmol), and 346 g of DMAc were used. Polyimide resin 7 was obtained. The obtained polyimide resin 7 was subjected to ¹ H NMR measurement, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that the imidization had progressed completely.
Resin composition 12 was prepared in the same manner as in Example 2, except that polyimide resin 7 was used instead of polyimide resin 1 in the resin composition of Example 2.
Using the resin composition 12, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 2.

(Example 13)
In the synthesis of the polyimide resin of Example 1, instead of using TMPBP-TME (23.19 g, 37.5 mmol), PMDA (4.38 g, 20.1 mmol), and BTDA (3.02 g, 9.4 mmol), as well as TFMB (15.00 g, 46.9 mmol), and DABPAF (7.35 g, 20.1 mmol), TMPBP-TME (31.98 g, 51.7 mmol), PMDA (1.25 g, 6.7 mmol), as well as TFMB (9.20 g, 28.7 mmol), and DABPAF (10.52 g, 28.7 mmol) were used, and 350 g of DMAc was used. Except for this, a polyimide resin was synthesized in the same manner as in Example 1, and polyimide resin 8 was obtained. The obtained polyimide resin 8 was subjected to ¹ H NMR measurement, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that the imidization had progressed completely.
Resin composition 13 was prepared in the same manner as in Example 2, except that polyimide resin 8 was used instead of polyimide resin 1 in the resin composition of Example 2.
Using the resin composition 13, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 2.

As shown in Table 2, the resin compositions of Examples 5 to 13 of the present invention were found to be resin compositions that could form cured films with a high tensile modulus of elasticity of 4.5 GPa or more by heating at low temperatures of 200°C or less, while also having excellent irregularity embedding properties. The cured films of the resin compositions of Examples 5 to 13 of the present invention also had a low linear thermal expansion coefficient.

(Example 14)
A polyimide resin was synthesized in the same manner as in Example 1, except that, instead of using TFMB (15.00 g, 46.9 mmol) and DABPAF (7.35 g, 20.1 mmol), TFMB (20.36 g, 63.6 mmol) and 4,4'-diaminodiphenyl ether (ODA, manufactured by Seika) (0.67 g, 3.3 mmol) were used, and 292 g of DMAc was used. Polyimide resin 9 was obtained by synthesizing the polyimide resin 9. ^1H NMR measurement was performed on the obtained polyimide resin 9, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that imidization had progressed completely.
Resin composition 14 was prepared in the same manner as in Example 2, except that polyimide resin 9 was used instead of polyimide resin 1 in the resin composition of Example 2.
Using the resin composition 14, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 3.

(Example 15)
In the synthesis of the polyimide resin of Example 1, TFMB (15.00 g, 46.9 mmol) and DABPAF (7.35 g, 20.1 mmol) were used instead of TFMB (19.29 g, 60.2 mmol) and ODA (1.34 g, 6.7 mmol), and 290 g of DMAc were used, but the procedure was the same as in Example 1 to synthesize a polyimide resin and obtain a polyimide resin 10. The obtained polyimide resin 10 was subjected to ¹ H NMR measurement, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that the imidization had progressed completely.
Resin composition 15 was prepared in the same manner as in Example 2, except that polyimide resin 10 was used instead of polyimide resin 1 in the resin composition of Example 2.
Using the resin composition 15, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 3.

(Example 16)
In the synthesis of the polyimide resin of Example 1, TFMB (15.00 g, 46.9 mmol) and ODA (4.02 g, 20.1 mmol) were used instead of TFMB (15.00 g, 46.9 mmol) and DABPAF (7.35 g, 20.1 mmol), and 281 g of DMAc were used, but the procedure was the same as in Example 1 to synthesize a polyimide resin and obtain a polyimide resin 11. The obtained polyimide resin 11 was subjected to ¹ H NMR measurement, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that the imidization had progressed completely.
Resin composition 16 was prepared in the same manner as in Example 2, except that polyimide resin 11 was used instead of polyimide resin 1 in the resin composition of Example 2.
Using the resin composition 16, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 3.

(Example 17)
In the synthesis of the polyimide resin of Example 1, instead of using TFMB (15.00 g, 46.9 mmol) and DABPAF (7.35 g, 20.1 mmol), TFMB (20.36 g, 63.6 mmol) and 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane (HFBAPP, manufactured by Seika Corporation) (1.74 g, 3.3 mmol) were used, and DMAc was changed to 299 g. A polyimide resin was synthesized in the same manner as in Example 1 to obtain polyimide resin 12. ¹ H NMR measurement was performed on the obtained polyimide resin 12, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that imidization had progressed completely.
Resin composition 17 was prepared in the same manner as in Example 2, except that polyimide resin 12 was used instead of polyimide resin 1 in the resin composition of Example 2.
Using the resin composition 17, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 3.

(Example 18)
In the synthesis of the polyimide resin of Example 1, instead of using TFMB (15.00 g, 46.9 mmol) and DABPAF (7.35 g, 20.1 mmol), TFMB (20.36 g, 63.6 mmol) and bis(4-(3-aminophenoxy)phenyl)sulfone (BAPS-M, manufactured by Seika Corporation) (1.45 g, 3.3 mmol) were used, and 297 g of DMAc was used. A polyimide resin was synthesized in the same manner as in Example 1 to obtain polyimide resin 13. ¹ H NMR measurement was performed on the obtained polyimide resin 13, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that imidization had progressed completely.
Resin composition 18 was prepared in the same manner as in Example 2, except that polyimide resin 13 was used instead of polyimide resin 1 in the resin composition of Example 2.
Using the resin composition 18, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 3.

(Example 19)
In the synthesis of the polyimide resin of Example 1, instead of using TFMB (15.00 g, 46.9 mmol) and DABPAF (7.35 g, 20.1 mmol), TFMB (20.36 g, 63.6 mmol) and bis(4-(4-aminophenoxy)phenyl)sulfone (BAPS, manufactured by Seika Corporation) (1.45 g, 3.3 mmol) were used, and 297 g of DMAc was used. A polyimide resin was synthesized in the same manner as in Example 1 to obtain polyimide resin 14. ¹ H NMR measurement was performed on the obtained polyimide resin 14, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that imidization had progressed completely.
Resin composition 19 was prepared in the same manner as in Example 2, except that polyimide resin 14 was used instead of polyimide resin 1 in the resin composition of Example 2.
Using the resin composition 19, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 3.

(Example 20)
In the synthesis of the polyimide resin of Example 1, instead of using TMPBP-TME (23.19 g, 37.5 mmol), PMDA (4.38 g, 20.1 mmol), and BTDA (3.02 g, 9.4 mmol), as well as TFMB (15.00 g, 46.9 mmol) and DABPAF (7.35 g, 20.1 mmol), TMPBP-TME (14.49 g, 23.4 mmol), PMDA (4.38 g, 20.1 mmol), and BTDA (7.55 g, 23.4 mmol), as well as TFMB (20.36 g, 63.6 mmol) and ODA (6.70 g, 3.3 mmol), were used, and 267 g of DMAc was used. Except for this, a polyimide resin was synthesized in the same manner as in Example 1, and polyimide resin 15 was obtained. The obtained polyimide resin 15 was subjected to ¹ H NMR measurement, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that the imidization had progressed completely.
Resin composition 20 was prepared in the same manner as in Example 2, except that polyimide resin 15 was used instead of polyimide resin 1 in the resin composition of Example 2.
Using the resin composition 20, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 3.

(Example 21)
Resin composition 21 was prepared in the same manner as in Example 20, except that in the resin composition of Example 20, 10 parts by mass of the epoxy compound was added instead of 3 parts by mass per 100 parts by mass of the polyimide resin.
Using the resin composition 21, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 3.

(Comparative Example 5)
In the synthesis of the polyimide resin of Example 1, instead of using TMPBP-TME (23.19 g, 37.5 mmol), PMDA (4.38 g, 20.1 mmol), and BTDA (3.02 g, 9.4 mmol), as well as TFMB (15.00 g, 46.9 mmol) and DABPAF (7.35 g, 20.1 mmol), TMPBP-TME (41.40 g, 66.9 mmol), and TFMB (21.43 g, 66.9 mmol), and 356 g of DMAc were used, except that a polyimide resin was synthesized in the same manner as in Example 1 to obtain polyimide resin C2. ¹ H NMR measurement was performed on the obtained polyimide resin C2, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that imidization had progressed completely.
Comparative resin composition 5 was prepared in the same manner as in Example 2, except that in the resin composition of Example 2, polyimide resin C2 was used instead of polyimide resin 1, and no epoxy compound was added.
Using the comparative resin composition 5, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 3.

(Comparative Example 6)
A polyimide resin was synthesized in the same manner as in Comparative Example 5, except that the amount of DMAc was changed from 356 g to 251 g in Comparative Example 5, to obtain Polyimide Resin C3. The obtained Polyimide Resin C3 was subjected to ¹ H NMR measurement, and it was confirmed that the signals derived from the carboxy protons and amide protons of the polyamic acid had disappeared, that is, it was confirmed that the imidization had progressed completely.
Comparative resin composition 6 was prepared in the same manner as in Example 2, except that in the resin composition of Example 2, polyimide resin C3 was used instead of polyimide resin 1, and no epoxy compound was added.
Using the comparative resin composition 6, a cured film of the resin composition was produced, and a substrate for evaluating the embeddability of irregularities was prepared and evaluated in the same manner as in Example 1. The obtained evaluation results are shown in Table 3.

It was revealed that the resin compositions of Examples 14 to 21 of the present invention are resin compositions that are capable of forming a cured film with a high tensile modulus of elasticity of 4.5 GPa or more by heating at a low temperature of 200° C. or less, and have excellent irregularity embedding properties. The cured films of the resin compositions of Examples 14 to 21 of the present invention also had a low linear thermal expansion coefficient.
In contrast, Comparative Example 5, which is a resin composition including only tetracarboxylic acid residues represented by formula (a-1) as the tetracarboxylic acid residues and only diamine residues represented by formula (b-1) as the diamine residues in the structural units and including a polyimide having the same weight-average molecular weight as in the Examples and a solvent, had a low linear thermal expansion coefficient, but the tensile modulus was low at 3.1 GPa and the irregularity embedding property was also poor.
Comparative Example 6, which is a resin composition including only tetracarboxylic acid residues represented by formula (a-1) as the tetracarboxylic acid residues and only diamine residues represented by formula (b-1) as the diamine residues in the structural units and including a polyimide having a weight average molecular weight higher than those of the Examples, and a solvent, had a tensile modulus similar to that of the Examples, but had poor irregularity embedding properties.

REFERENCE SIGNS LIST 1 semiconductor substrate 2 protective film 3 first conductor layer 4 interlayer insulating film 5 photosensitive resin layer 6A, 6B window 7 second conductor layer 8 surface protective film 11 IC chip 12 metal wiring 13 molding resin 14 insulating film 15 metal wiring 16 metal wiring 17 insulating film 18 barrier metal 20 solder bump

Claims (15)

A resin composition comprising a polyimide resin, an organic solvent having a saturated vapor pressure of 0.5 kPa or less at 20°C, and an epoxy compound, the resin composition producing a cured film having a tensile modulus of elasticity of 4.5 GPa or more as measured by the following evaluation method.
[Evaluation method]
The resin composition is spin-coated onto a glass substrate having a polyimide film (UPILEX (registered trademark) 125S, [5,5'-biisobenzofuran]-1,1',3,3'-tetraone-1,4-phenylenediamine polycondensate, manufactured by UBE Corporation) attached thereto. The spin-coating conditions are adjusted so that the thickness of the cured film of the resin composition finally obtained is 40 μm±5 μm. After spin-coating the resin composition, the substrate is heated on a hot plate at 40° C. for 8 minutes, then at 80° C. for 8 minutes, and then at 130° C. for 8 minutes to dry the solvent. After drying, the substrate is placed in an oven and heated in the atmosphere at 200° C. for 1 hour, allowed to cool to 25° C., and the cured film of the resin composition is peeled off from the substrate to produce a cured film.
A test piece of the cured film cut into a size of 10 mm wide x 150 mm long is used to measure the tensile modulus at 25°C, a stretching speed of 50 mm/min, and a grip distance of 100 mm using a tensile tester. The polyimide resin contains a structural unit represented by the following general formula (PI):

(In general formula (PI), A represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and B represents a divalent group which is a diamine residue having an aromatic ring or an aliphatic ring.)
The tetracarboxylic acid residue includes a tetracarboxylic acid residue represented by the following formula (a-1) and a tetracarboxylic acid residue represented by the following formula (a-2), and may include a tetracarboxylic acid residue represented by the following formula (a-3):
The diamine residue includes a diamine residue represented by the following formula (b-1), and may include at least one diamine residue selected from the group consisting of diamine residues represented by the following formulas (b-2) to (b-6):
In the total tetracarboxylic acid residues, the content of tetracarboxylic acid residues represented by the following formula (a-1) is 30 mol % to 95 mol %, the content of tetracarboxylic acid residues represented by the following formula (a-2) is 5 mol % to 40 mol %, and the content of tetracarboxylic acid residues represented by the following formula (a-3) is 0 mol % to 35 mol %,
The resin composition according to claim 1, wherein the content of the diamine residue represented by the following formula (b-1) is 50 mol% to 100 mol%, and the content of at least one diamine residue selected from the group consisting of diamine residues represented by the following formulas (b-2) to (b-6) is 0 mol% to 50 mol%, in all diamine residues.
(In formulas (a-1) to (a-3) and formulas (b-1) to (b-6), * represents a bond.) The resin composition according to claim 1 or 2, which has a viscosity of 3,000 mPa·s to 7,000 mPa·s at 25°C when the solid content other than the organic solvent is 7 to 13 mass%. The resin composition according to claim 1 or 2, wherein the epoxy compound includes an epoxy compound having three or more epoxy groups in one molecule and having a glycidyl amine moiety. The resin composition according to claim 1 or 2, wherein the organic solvent having a saturated vapor pressure of 0.5 kPa or less at 20°C is at least one selected from the group consisting of N,N-dimethylacetamide, benzyl acetate, γ-butyrolactone, and isophorone. A step of applying the resin composition according to claim 1 or 2 onto a substrate and drying the composition to form a coating film;
A method for producing a cured film, comprising a step of heating the coating film to form a cured film. The method for producing a cured film according to claim 6, wherein the temperature to which the coating film is heated is 150°C or higher and 240°C or lower. A cured film obtained by curing the resin composition according to claim 1 or 2. The cured film according to claim 8, having a linear thermal expansion coefficient of 40 ppm/°C or less at 100°C to 150°C. An insulating film produced using the cured film described in claim 8. A protective film made using the cured film described in claim 8. An electronic component comprising the insulating film of claim 10. An electronic component comprising the protective film of claim 11. An electronic component comprising an IC chip, a molding resin surrounding at least the IC chip, and a wiring layer including the insulating film and wiring of claim 10. The electronic component according to claim 14, wherein the molding resin is a cured product of an epoxy resin composition.